You can not upload to a specific imgur account.
If I start the upload I get the screen found in
I tried to find the issue by my own and what I got was the error shown in
I also did some research and the solution lies here on stack overflow
Windows 10 (probably all)
thanks for doing some research, but what should the solution on stackoverflow bring?
That entry is extremely old... Greenshot was working fine for a longer time and recently Imgur must have changed something.
Anyway, this is a duplicate of BUG-2235, where I already presented a solution.
The 1.2.10 release will be available in one or two weeks.