It is a popular extension so I my bet would be that a long-term solution is on its way.

I have the exact same issue after upgrading k2 to version 2.8.0. I have cleared the cache and updated Joomla to 3.8.2. I don't have JA K2 Filter in my website. I use Styleware Filter for K2. I tried disabling that, cleared the cache, but the backend k2 fields are not showing. Its just empty.

This only happens when I go to: Backend -> K2 -> Extra Fields. I have over 20 extra fields overall, and none of them are showing.

But, when I edit the articles or create articles in those categories, the extra fields are visible in the editing screen tab. Also the extra fields shows in the article body.

The backend Extra Fields Groups page shows the groups created.

Its only the Backend -> K2 -> Extra Fields page that is empty. Very unusual.

Thanks,
Neel.

Hello Neel,

Did you check your browser's developer tools' console tab for any issues?