Ok, I found the answer. It’s a quite stupid copy/paste mistake. The name of my nonce_field was not unique. I had already created another nonce from the same plugin but another file. Therefore the basename(__FILE__) value was different leading to a different nonce. All I had to do was change the the name of the field to something unique and it worked.
Related Posts:
- My custom write panels won’t save data. What am I missing?
- Why do Metabox use Nonces?
- when saveing $meta_box i get Undefined index error
- Create more Meta Boxes as needed
- Passing error/warning messages from a meta box to “admin_notices”
- How to HIDE everything in PUBLISH metabox except Move to Trash & PUBLISH button
- Removing panels (meta boxes) in the Block Editor
- How to make open/closed and hidden/shown metaboxes status saved on a per-post basis?
- How To Remove The “+ Add New Category” Link From A Category Metabox
- How can I create a taxonomy meta-box with search suggestions but no new terms input?
- How Does WordPress Remember Metabox Positions?
- How to Add Reminders/Notes to New Post Meta Boxes
- How to reorder meta box position?
- Custom Meta Boxes: multiple fields within a repeatable field
- Save checkbox value in metabox
- How to group meta boxes on the post edit page
- get registered metaboxes by post type or post ID
- Remove metabox from specific page template in admin
- Is there a filter/action to add content to WP admin metaboxes?
- Attach Files Metabox
- How do I create a meta box for dates?
- esc before saving or before displaying does it matter?
- Add a meta description to home page?
- how to sanitize checkbox input?
- Display list of tags as drop down menu or radio buttons in a meta box?
- Set height of the categories meta box in post dashboard
- Undefined index: at_nonce in custom post metabox
- Save checkboxes of a metabox with a foreach loop (invalid argument)
- Get image captions for images on gallery post format metabox
- Multiple Checkboxes Metabox
- Adding Metaboxes – so much code is there a shorter DRY way?
- I need a Simple image uploader with a simple screen. WP default has too many options.
- Show or hide custom meta box not work with Gutenberg
- How to save multiple metaboxes?
- TinyMCE with custom buttons on a meta box
- How do i hide the auto-generated custom field that’s created when update_post_meta() is called?
- How to search by metadata using REST API
- Alternative to esc_textarea
- Automatically add a tag according to custom metadata
- How to add categories to page editor?
- Having trouble getting my meta data to save
- Display meta box on front end
- Show how many images are attached to a post/page on compose page
- metabox wordpress show in frontend
- Metabox context for page post type
- How to use MarkDown in a custom textarea field?
- How to use get_post_custom function on the blog page?
- Multiplicate entry on update_post_meta
- Populate meta select box with child pages
- Problem with meta box in Links
- Post Meta not saving when have empty post
- Remove ShareDaddy meta box from Pages only
- On click hide group of metabox, similar to screen options checkbox?
- How to make a stand-alone button to the post edit view
- Custom Meta box only returns most recent value on page
- wp_editor loses data, perhaps an html_entity_decode problem?
- How to list all tags as radio buttons in a meta box?
- How to position user meta data field
- Display Content if Meta Checkbox is checked?
- Output from Meta Box Array
- add_post_meta() & update_post_meta()
- How to verify nonces in bulk?
- MetaBox with Editor instead of textarea – html not saved [closed]
- Use meta boxes inside an archive page template for Woocommerce
- conditionally echo in meta box data loop
- Getting metabox value?
- Meta box does not save or update
- Meta Box multi checkbox in template
- Post Excerpt field only showing for default administrator
- remove a single post_meta
- Is ‘repeatable’ a field type for meta boxes?
- how to log in to WP if the “Log in” link under Meta is missing
- Custom loop attached to link
- Getting metabox value within a shortcode?
- post meta – problem : copy the same meta for all the articles
- ACF – Hiding metaboxes through screen settings doesn’t work
- Add metabox to pages that use custom template in WordPress
- how can I make this metabox area
- How to Edit & Update meta_box values from Front-End user Form
- Featured Gallery to custom post type
- Can’t get meta values to save
- Unable to save multiple images in wordpress
- Custom WP Meta Box – Use data from within the post screen inside meta box
- How to show select_advanced content instead of ID?
- Is this Edit Post Screen?
- Custom meta box repeated field
- Using Meta Boxes in a Custom Page Template
- A correct hook for saving meta boxes data
- update_post_meta does not work
- Hooking into the Meta Boxes (Name/Web Address/Description) on the ‘Add New Link’ Page
- Custom carousel with meta box data
- Adding a Custom ‘Now’ button under ‘Published on’ header to return current date and time
- Adding meta boxes to custom post type
- Select Options Meta Data is Not Updating in Edit Meta Box
- Meta boxes not showing up
- Metabox doesn’t retain values
- How do I create a Meta box that can be repeated? (with an image section and text area)
- How can i remove blank area caused by theme’s post meta boxes?
- Need help, Passing variables with get_post_meta
- Metaboxes – why they don’t render php in expected manner?