My problem has been solved.
I noticed that when I used the same Evernote account, but through a different Windows profile on the same device, the problem did not occur. (...my dear wife was the test. OK it is a bit unknowingly risky, but soit we've been together for 44 years so some things are already possible lol)
With the lead in my shoes, I logged out and clicked on the dialogue box... my data could go. (...7445 notes...sic...) Immediately afterwards, within a minute, without rebooting, I logged in again via the icon on my taskbar ...surprise...all the data was still there, and in the task module no green circle, and ...a version number higher (10.64.5).
All systems are running smoothly. 😃