Import Exchange's Simple Shift UDT - failure

I wish to try out Phillip Bourner's Simple Shift UDT for Perspective. I've downloaded it and when I try to import it into the 8.1.25 trial licence gateway I get

Failed to import project.
Gateway reported that it could not import project.

I also tried unzipping and importing the .gwbk file but that failed as well.
I've used other Exchange resources without difficulty.

Any ideas before I bother Phillip directly?

Well, gateway backups aren't projects. Phillip likely did this because tags and UDTs aren't part of projects. You will need to restore into a fresh gateway install, then export the pieces. (Which is what Phillip should have supplied, as separate JSON files.)