Is it possible to return a user attribute in the ID token using protocol mappers?

I have a user that has a custom attribute called "accountId" and a value is assigned to it. I checked in the USER_ATTRIBUTE table (mysql) and the values are properly assigned.

I created a protocol mapper. In that I set the protocol type as "User Attribute" and entered the key "accountId" as both the User Attribute and Token Claim Name and switched on both "Add to ID Token" and "Add to Access Token".

I simply cant get this accountID attribute value returned in the ID Token nor Access Token.

Basically I need to return the user attributes in the ID Token / Access Token. Is it possible?

Regards,

Kalinga