Finally got a bit more time to look at this — okay, good to know the keys only work on specific versions, and weird that it’s not mentioned anywhere on the license page, and that there’s not a more useful error message when trying to activate a version of perch.
Will a newly bought Perch 3 license key work with Perch 2? As far as I can tell, in order to run the automatic upgrades, I need to first upgrade from Perch 1 to 2 before moving on to 3, but I can only buy a license key for the newest version.