SharePoint not checking document back in after discarding check out.

I have a word document in SharePoint Online that I have checked out to make changes. Once my changes were made, a pop up came up saying that I had the original version checked out and then asked if I wanted to discard the checkout. I clicked yes. Isn't it supposed to check the document back in automatically after I click yes to discard the document? In my case, it stayed checked out. I am unable to check it back in. Can you help?

Thanks!