Hi Matt,
Check post #577
https://www.zen-cart.com/showthread....69#post1381369
I spent a day going round in circles and then I added &sandbox=1 as suggested and this displayed new fields I'd never seen before. With mine the Live Merchant Token was incorrect. I obtained the correct one from my Square Developer Dashboard and after saving and editing again so the location was refreshed everything started working for me.
Brent
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