Hey, I got the same error and resolved it by going to Settings -> My Info -> Address and removing the special character (in my case a ß) and going back to the poposal afterwards.
I hope this helps!
I had the same issue.
It was fixed when I filled out my address details. I guess empty address fields cause that problem as well and not just special characters. Cheers.
Hey upwork, you should put this bug on your highest urgency level.
For an international platform this is very annoying. I have the same problem. Seems like because my name is written with an "ö". Now I can't use PayPal and have to use my Credit Card, which means I have to wait some days to verify.