works then doesn't work. runs in mobile mode instead of desktop mode so adding content or #Tags is impossible. Ghostery has fully allowed Pinterest for tracking its is NOT the problem, Poor programming and blame game...
Any detail you could give besides "works then doesn't work" would be helpful, such as your OS and Firefox versions, the URL of the page you're trying to save, and how (browser button, hovering Save button, context menu) you are invoking the add-on.
I am not sure what "runs in mobile mode instead of desktop mode" is supposed to mean. Are you running the extension on mobile Firefox? Also not sure what "adding content or #Tags" means; unless you mean entering hashtags in pin descriptions, tags aren't really a thing on Pinterest.
I did not mean to come across as "blaming" Ghostery; I have mentioned it in replies becuase we've had at least one case of a user (in these reviews) who mentioned it as another installed add-on. I will count you as a reporter who is also using it, unless that's wrong.