WordPress Plugin version 19.4.0 has an issue that prevents future upgrades.
When you upgrade to version 19.4.0 (or afterwards) from version 19.3.5 (or below), you might encounter this error: "The plugin social-polls-by-opinionstage/opinionstage-polls.php has been deactivated due to an error: Plugin file does not exist."
The issue has already been resolved, however if you have already installed the 19.4.0 version you may still face the issue.
How to fix it:
- Refresh (or go to) plugins screen
- Click "Activate" on "Poll, Survey, Quiz, Slideshow, Form & Story Article" plugin
- New version should be installed and issue fixed