Or more specifically "Cannot register Windchill 10.1 M020 from Creo 2.0 M070 Server Registry"
This issue started as a lost license, and it would not reconnect. On the road to resolving this problem, I tried creating a New Registry, but it would fail: "invalid server location. please change the "location" field and try again"
There was a similar Acticle in support (CS156001) about when the language was set to Turkish and this same problem would happen. So knowing this, I added "set PRO_LANG=english" into our script and this solved the issue (our parent company is swiss/german, so once in a while things here change to swiss/german).
So to recap:
If the server you know exists can not be found, try adding the environment variables:
set LANG=english (or your specific language insalled)
set PRO_LANG=english
Hopefully this helps other having the same problem...