Having issues as of recent with uploading a Thumbnail image on a portfolio item. The option is there to add thumbnail, but when clicking on “Add Thumbnail” button – the page refreshes, but there is no option or pop-up to select a photo from media library.

I have tried doing this in different browsers, and on different devices – same issue persists. When clicking on the “Add Thumbnail” button, the page refreshes and nothing else happens.

Have been trying for about 4 days now.