Hello,
the Boxtal's support is deaf and turns in circles ...
Yes, unfortunately, we know that. That's why we do not provide support on that plugin anymore.
It is not our mission to do that and your issue is just with your credentials and the type of account (in production or in sandbox).
If the plugin can retrieve the categories, then your account is OK.
That's all we can tell you because we are not Boxtal and that's not our accounts.
We can provide you help regarding HikaShop but our "boxtal" plugin is working good, as long as the account is activate in Boxtal.
Regards,