install square extension

from opencart marketplace, i search for square, download one that works for OC3037. (php version is 7.3)
in extension installer, i upload square.ocmod.zip (by iSenseLabs) [cloud] and non-cloud version.
extension modifications show nothing. (nothing for me to refresh)
i go to extension > extension > dropdown payments > find square -> install
when i click 'edit' after installing, i get:
"This page isn’t working <my URL> is currently unable to handle this request.
HTTP ERROR 500"

what can i do now?
thanks

What is in your server error logs? It should say what error it is running into.
Also you might want to contact iSenseLabs.
Mike