I have the same issue and I am in the process of diagnosing the cause. I now know the following: When I run in Safe mode and use only Apple software plus Outlook, Word and Excel, the issue does not occur. However, the issue occurs after sharing my screen using TEAMS. I also believe it occurs when using Screen Capture from a third party software, in my case using Camtasia. In addition to not being able to launch adds, I find that certain full desktop screens will not access the top menu bar.
The immediate solution is to press F3 to open the desktops on top and then click on the current desktop giving the issue and it resolves itself. However, it will continue to re-occur until you reboot your computer. At that time, it will run fine until you use a screen-sharing or capturing third-party software.
I was told yesterday by Apple that I should contact all the third-party software companies so that they resolve their problems with iOS 27.