Thank you for any advices!
I repeat:
I have got an old application AIA-file (created on May 2021), that works OK since that time. I have got also an old APK-file (of this application), that was created AT THE SAME TIME (May 2021). I CAN install this file (APK) on my smartphone with Android 13 without any problems...
BUT
If I build a new APK-file TODAY (of the same application, without making any changes!), I can't install it on my smartphone.
Sorry, but it looks, that there is some problem (?) at MIT App Inventor...
I'm sending a link to my Google Drive directory with three files. You can find there also a screenshot with error-message from my smartphone (polish): DELETED
PS
- My smartphone is Samsung S21 + Android 13.
- My wife's smartphone: Samsung with Android 13.
- My son's smartphone: Samsung with Android 11.
EDIT:
Probably the "PushNotification" extension caused my problem. I have deleted it and now I can install my APP on my smartphone.
Anyway, thank you for your advices and sorry for disturbing on your community!