When I'm in the Items list, if I click on the title of an item, it opens up in the editor as expected. However, if I click on the Feature buttons to change it from the red X to the green check, I end up in at the Joomla control panel and the change isn't made. It's the same if I click Unpublish, or if I enable the checkbox beside an item and click the Toggle Featured State button.

I'm new to K2, so any ideas on how to solve this would be appreciated.

Hello,

Which K2 and Joomla! versions are you using?
Any 3rd party K2 extensions?

Joomla 3.8.3
K2 2.8.0
No additional K2 extensions

Can you check on your browser's developer tools' console tab for any JavaScript issues?

Inexplicable. Now it's working. I don't think I changed anything. I can't explain.
Thanks anyway.
Erich

This is odd,
Let me know if you find the culprit.