Pop up in Edge blocked but not showing as blocked in address bar?!

We had some sw on a back end app server and on Edge it was blocking a pop-up of a pdf when we clicked an 'Ok' button. This was highlighted in the address bar which shows and quickly disappears. Pop-ups are blocked by GPO and I can't change that currently. There is nothing in the allowed or blocked list.

We've had a new version of the sw installed on the back end server and now clicking on 'Ok' does not load the pop-up (as expected) but now we don't even get anything showing the fact that a pop-up was blocked. 

I am told by the sw supplier that Edge eventually stops telling you its blocked a pop-up in the address bar. Is this really the case? Not heard this before and how can I check that Edge is blocking but not telling me?

Thanks staro