To investigate the issue, you can follow these steps:
- Check site URL in settings – General, WordPress Address (URL) and Site Address (URL)
If you have WordPress in a directory, make sure the installation process is right based on https://wordpress.org/support/article/giving-wordpress-its-own-directory/ - Check .htaccess file to make sure there is no wrong rule. Check the documentation link on step 1.
- Re-install WordPress from admin dashboard – Updates.