Cannot save changes to preferences

When I click ‘Save Changes’ in the lower right corner, the page reloads with

403
Forbidden
Access to this resource on the server is denied!

I tried changing the video player size through the php file at
/wp-content/plugins/youtube-embed-plus/youtube.php
but they did not affect the video size.
I also tried setting permissions to the file for write:everybody.

On the webpage, the player is the same width as the 3 columns but I want it to be a maximum of 840 x 472.

• This topic was modified 5 years, 5 months ago by jolanxbl.