I don't know why, but it i can start it again without the error message.
BUT: All OTPs are now wrong !!!!
I tried login different sites but unsuccessfully. I compared the OTPs from the Windows app and Android app. They are different. On windows they are wrong and on Android still correct. The URL is the same, no differences.
UPDATE: Now i got 0x803f8001 again. Before that i figured out the reason of the wrong OTPs. After the Windows update the time was suddenly wrong! The time was back to daylight saving time.