When that error happens that means it is an edge case type of issue. Not having access will make this bit more difficult to troubleshoot.
The first thing, I’ll need a screenshot of the System widget on the Connections : Dashboard admin page.
Open the Connections : Manage admin page that has the error. Hit Ctrl+U to view that page source. Save the page source as a txt file. I’ll need a copy of that file.
Lastly, on line 1509 of this file:
var_dump( $img_path );var_dump( file_exists( $img_path ) );
This will cause quite a bit of error code text to show on the page. I’ll need a copy of error code text it displays. After you’ve copied the text, you can remove the code.
When you add/update plugins, does WordPress prompt you for the FTP use/pass?
Can you upload images to the WordPress Media Library without an errors?