Sub-panels can also be tricky if they're not properly setup with neutrals & grounds separated. The panels usually come with a screw in place that bonds the neutrals & grounds. That bonding should only occur in the main panel (technically inside the main disconnect, but that's usually the main panel). So, in a sub-panel the screw needs to be removed and separate bus-bars must be used for neutrals & grounds.
If your garage sub-panel has neutrals & grounds mixed together on the same bus-bars, you could wind up with stray current on the ground that the EVSE doesn't like.
Electrician should be able to straighten it out for you.
If your garage sub-panel has neutrals & grounds mixed together on the same bus-bars, you could wind up with stray current on the ground that the EVSE doesn't like.
Electrician should be able to straighten it out for you.