One last update, the "signout" option and log back in to Win11 works. Probably the problem is sleep mode is a little flaky on this computer I built myself. But it never happened until the last app update.

I can't really complain because I have been using this HD Prime with Xfinity cable card since ...

No, I always close the HD app when I put computer to sleep. I just tried again after sleep and got the Null error. Instead of restarting the computer, I instead "signed off" and signed back in. That worked and is easier than restarting. This only started with the last update a few days ago. Only ...

When I started computer this morning, the Homerun app worked normally. When it came out of sleep mode, it got the null error again. Restarted the computer and it worked again. Not a fix, but at least it works. I have a fast boot drive, so rebooting is not that big of a deal.

I fixed it by installing a "preview update" of Windows. Normally I don't install the preview updates, but this time it worked.

HD Homerun Prime with Xfinity cable card. Was working fine yesterday, now the Windows app crashes with this message "Null strings man not be marshaled in Windows Runtime arguments. Parameter name: sourceString" Android apps, no problem. Firestick app no problem. Google TV OS, no problem. Other ...