I had this problem in the past when they revamped everything. I found that when I want to cast the tab, I couldn't just click "cast". I had to click the drop down menu that says "cast this tab" and then click "cast". I have no idea why that works instead now. Hope that makes sense.

Hi Nancy! I'm sorry to hear that you are experiencing issues - I am going to send you an email to see if I can get some more information from you and help you troubleshoot this issue.