All plugins deactivated due to error

@Jutta, this is a hard question to answer. Many unknowns.
What you may do is to understand the error.
WordPress may have the error log.
Set define( 'WP_DEBUG_LOG', true ); in your config file, and then you need to check the results as per this article.

Note that this allows you to write to /wp-content/debug.log

A web server may have the error log.
Work with your Hosting support if WordPress error log cannot help.
This is not strictly WordPress item, so I will be a fish in there.

You can work on both these to understand your problem better.
Please update your question with more details once you find that.

You may even consider accepting my answer if you like it, or if you think it is helpful, because this is a general approach what to do. We may create additional questions for specific errors we may find on your web server.

Related Posts:

  1. How to catch/what to do with a WP Error Object
  2. What are the best practices for updating?
  3. Is there a plugin that will override the “Error establishing a database connection” message? [closed]
  4. How to eliminate weird 404 errors in wp-admin?
  5. Loading external page template and enqueue script from plugin causes 403 forbidden error
  6. PHP Deprecated: Non-static method should not be called statically
  7. Plugins error (Use roles and capabilities instead) on latest version, multisite
  8. WordPress error – PHP Fatal error: Uncaught Error: Call to undefined function register_block_type_from_metadata()
  9. Plugin.php: PHP Notice: Undefined offset: 0 in
  10. “Are you sure you want to do this?” when deactivating all plugins in WordPress 4.3.1 [closed]
  11. How should I handle errors within a plugin?
  12. An Unexpected HTTP Error occurred during the API request
  13. Seaweed Plugin not working
  14. Unable to activate wordpress importer after installing it
  15. Weird problems after recovery from security breach
  16. Error in the wp-config.php file: PHP Fatal error: Uncaught Error: Unknown named parameter (PHP 8.0)
  17. Can a plugin still effect a site even after deletion?
  18. Accessing GET variable named ‘error’
  19. Error handling a plugin with exceptions
  20. Post-terms-order PHP errors after update
  21. Call to undefined function get_userdata in user.php
  22. Only Homepage not loading properly
  23. One of my plugins broke when I tried to update it, how do I safely uninstall it?
  24. Images not showing after changing wp-content folder name
  25. WooCommerce Checkout Error [closed]
  26. CSV file generation failing
  27. Plugin: Google Analytics for Dashboard error – Timestamp is too far from current time
  28. How to redirect a URL with parameters?
  29. Problem using Press-this book marklet
  30. Python with wordpress plugin
  31. Uncaught TypeError: jQuery(…).flipster is not a function in wordpress
  32. WordPress site periodically goes down
  33. Deactivating all plugins and reactivating one by one, fixes conflicts. Why?
  34. WordPress shows error related to allow_url_fopen
  35. Unable to get WP_DEBUG, WP_DEBUG_DISPLAY, WP_DEBUG_LOG to work
  36. Get errors from WP_Error to different variables
  37. help with my wordpress website
  38. HTTP 500 error after plugin install
  39. Can’t activate Plugin: unexpected T_STRING, expecting T_FUNCTION [closed]
  40. Plugin getting Cannot modify header information errors
  41. WP-nivo-slider Producing Error “Cannot modify header information – headers already sent by …”
  42. XML Sitemap Generator can’t notify google and bing
  43. After updating the WordPress getting a syntax error in the console
  44. React error #231with Custom Blocks after upgrade to WP 5.5
  45. There has been a critical error on your website – won’t fix no matter what
  46. UTF-32be error WordPress
  47. Elementor page builder plugin not loading up all the way? [closed]
  48. Getting error “Warning: mysql_query(): Can’t connect to local MySQL server through socket ‘FILEPATH/cccatalog-plugin.php on line 1656”
  49. Plugin showing error
  50. Classic, but puzzling “The uploaded file could not be moved”
  51. Plugin upgrade failing during unzip
  52. Problem after updating plugins
  53. Apparent errer when installing plugin
  54. How to get Facebook comment plugin in blog? [closed]
  55. Undefined index: ratings_score …/wp-postratings.php on line 994
  56. Strange Behavior on New Theme Points to Idiocy
  57. 404 errors when updating options in admin dashboard
  58. Error activating certain plugins
  59. All new plugins generating 311 chars of unexpected output?
  60. Error when adding extensions to wordpress version 5.9 with a DIVI install
  61. Replace old theme that understand old css (vcex_icon_box css_animation)
  62. WordPress fatal error from php protocol codes
  63. There has been a critical error on this website
  64. WP search box on page not finding .PDF files
  65. Changing wordpress/woocommerce notices default message to other languages (text)
  66. How to Fix WordPress multisite woocommerce 403 file error
  67. Critical Error after Updraft Restoration
  68. There has been a critical error on your website
  69. I can’t view the orders on the woocomerce dashboard with the brainblocks plugin
  70. Modifying server’s response to API endpoint
  71. Woocommerce functions in custom class, avoid errors
  72. ERROR message: “The site is experiencing technical difficulties. Please check your site admin email inbox for instructions.”
  73. Object of class WP_Error could not be converted to string in /formatting.php
  74. Error after installing the WordPress plugin updates
  75. White blank screen while adding or editing pages in wordpress
  76. Cannot modify header information – headers already sent during plugin activation
  77. WordPress website dont load CSS, JS and images
  78. WordPress error after installing plugin “Internal Server Error” [closed]
  79. Need Help Understanding Debug Log Errors
  80. ClassLoader.php issues after moving to a new host
  81. Plugin debugging with errors in activation routine
  82. WP default file upload hook not working if used in a plugin
  83. Warning: Illegal offset type in /var/www/html/wp-includes/option.php on line 1924
  84. A more elegant way to handle notices/warnings
  85. A plugin is giving me “You do not have sufficient permissions to access this page.” error
  86. Restore Category Base
  87. Plugin (smart archives reloaded) crashed site / no access on admin panel
  88. Custom Post type plugin breaking the front page shows dashboard?
  89. WordPress 3.5 install error
  90. Is there a plugin that will override the “Error establishing a database connection” message? [closed]
  91. Plugin won’t activate, fatal error (widget class not found)
  92. Plug-in (Slickr Flickr) works on local machine, but not server
  93. Theme causing SSL break on chrome
  94. The plugin generated xxx characters of unexpected output during activation
  95. WordPress Customer Reviews Error: Line 239?
  96. WordPress Plugin: Demon Image Annotation
  97. WordPress Plugins Error
  98. How to get an error message if a form is empty (plugin: Post for site) [closed]
  99. WordPress error Fatal error: Uncaught TypeError: Argument 3 passed to Automattic :get_setting_for_feature() [closed]
  100. Oxygen plugin wordpress stuck in loading sequence forever when trying to edit a page [closed]