Hello ,
I had the same problem with MySQL Flexible Server .
The deployment was failed with following error :
{
"status": "Failed",
"error": {
"code": "InvalidPrivateDnsZoneSubscription",
"message": "The subscription 'XXXXX-XXX-XXXX-XXX-XXXX' of the private DNS zone 'privatelink.mysql.database.azure.com' is in valid, it is not registered for '2'."
}
}
To resolve it , the unique provider to register is Microsoft.DBforMySQL on Private Dns Zone subscription.
Thanks
Jean Yves