Tab applications not working correctly


I’ve created tab applications before, but for some reason today I can’t add applications in the Folder Settings section. Clicking on the Add button does nothing and there is a message displayed which I’ve never seen before which says Before performing their Applications, enter the options below.

Please take a look at the attached image to see what I mean. Not sure why this is happening, and I would appreciate any help if someone knows what’s going on. Thanks.