i think a change is in order for square_webPay.
i'm a fan of line 173 in the core code. it requires an integer. square_webPay is not providing it.
am not sure what version you are running, but i will take a look at this next week, as i'm busy this weekend.
as a temporary solution, you can change 173 to:
PHP Code:
function zen_get_zone_code(int $country_id, $zone_id, ?string $default_zone = '')
i think that should work.
best.