Doing some backtracking on the OP's previous search for a tripod, Brad linked a Slik that I'm going to assume is the one the OP purchased.
https://www.24hourcampfire.com/ubbt...or-spotting-and-chronograph#Post17343402It has a 1/4"-20 mounting screw on the QR plate. I'd be utterly surprised if the Athlon spotter didn't have the same threads. Is it possible something else is going on like buggered up threads on one or the other?
ETA- or another possibility of a 1/4 to 3/8 adapter sticking to the QR plate when it was unscrewed from an optic, and now obviously makes it too big for the 1/4" threads on the Athlon. Pics of everything sure would help.