authme: 1.14_1.15-1.1.0
mc: 1.15.2
forge: 31.0.1

latest.log as there is no crash: https://gist.github.com/kreezxil/28d1b7229417fc1b778956c4977369f6

Thanks for reporting this, I am yet to test with the new 1.15.2 release, but from the looks of things, Forge must have removed their custom button. I have made a release here to use vanilla Minecraft's button - please find the release jar here in the meantime until approval on CurseForge.

https://github.com/Axieum/AuthMe/releases/tag/v1.14_1.15-1.1.1