I'm also having issues. Not having any luck getting the module to go in Zencart v2.0.1. I can't get the module authorized to my Square account. I have the OAuth Redirect URL correct... I'm putting in the correct Application ID and application Secret... If I try Sandbox mode I get a yello light for the module (not Green)... and if I click to edit the info I lose the module (screen goes blank and I have to delete the module and re-install it... If I use the production mode OAuth I get HTTP 500 error codes... says my domain cannot handle the request...
Any info on why and/or what I may be doing wrong greatly appreciated... I'm totally self taught with all this website and FTP and everything so laymean's terms work best with me... I don't understand some of the geek-speak termonolgy for these things