Hello,
Please configure credentials in the Joomla plugin manager side
It is not an error message ; it is an indication telling you that the "client id" information is not to be set-up in that part of the plugin but you have to provide this element via the Joomla plugin manager.
Failed to get/create the legal user for your main vendor.
Please check that you right set your MangoPay credentials in the plugin (Joomla site)
Please also check that your account have a valid published address
When you save the MangoPay configuration, the plugin try to get the main vendor from the platform or create if if not there.
If you got that error it means that the main vendor has not be created in the MangoPay platform.
It can be because of wrong credentials (please note that "sandbox" environment is also an important element)
It can be because of missing data from your HikaShop account since MangoPay need "Legal Representative" details and the plugin will get
your account default address for that (first name, last name, street, city, country).
Regards,