Hello castilo14004,
I found one 404 page, it’s the log in page, with the following JS error:
Failed to load resource: the server responded with a status of 404 (Not Found)
As you mentioned, you did a test for a conflict with a plugin, would you please do the same with your theme? Switch to a default WordPress theme and test if the 404 errors are there.
What PHP version you are using on your site?
i came up with an idea, which is deleting the all files of coursepress, but i lose all my work
You can try to delete and reinstall the plugin instead. The courses shouldn’t be lost, although please create a full back up of your site before doing this.
If after of of this you will have 404 pages, please enable WordPress debugging, place the following to the wp-config.php file:
define( 'WP_DEBUG', true );
define( 'WP_DEBUG_LOG', true );
define( 'WP_DEBUG_DISPLAY', false );
Visit one of the 404 pages, after that all errors will be saved in the debug.log file inside the /wp-content/ directory. Let us know the errors you see.
Kind Regards,
Nastia