I am getting the same error when trying to download untools 2.8.1. I have removed all of the clones on my machine, then performed the following steps:
-Cloned active environment
-Closed and reopened Pro
-Added untools 2.8.1 and confirmed it was installed by going to the Explorer directory. However it still showing the error that the untools module doesn't exist.
Is this a known issue for 2.8.1? Going to try installing untools 2.8 to see if the issue goes away.