When creating an event, the Attributes section displays this message, “There are no registrant attributes defined.”
There is a key that is incorrectly set in dbo.Setting table. There is a key named ParticipantAttrsUpgraded. It is set to true by default. I needs to be set to false. Execute the following SQL script against your CRM database to solve the problem.
SET [Value] = 'False'
WHERE Name = 'ParticipantAttrsUpgraded'