422
providers.provider_existsprovidersRule R8A provider with this code is already registered
Provider codes are unique across the install. Registering an existing code is refused rather than merged, so an operator cannot silently overwrite another provider's configuration.
Why the API refuses
WHEN RegisterProvider is executed with a code that is already registered, THE SYSTEM SHALL reject it naming the code field.
What to do
Use UpdateProvider to change the existing registration, or pick a different code.