unable to Enable subscribers to my record

Created new record type for subscriber

Added relationship with base record type

Eventhistory

eventType

event thread configured.

flowed below steps 

On the base record type, edit the record events configuration:

1. Go to Events.
2. Click EDIT.

3. Configure the following Subscriber properties:

there is no option to add subscriber record

and unable to see the subscriber icon on event history in summary view

 anyone implemented please post your suggestion 

@Everyone  we upgraded now to 25.1. 

while enabling subscriber am facing issue

a!eventHistoryListField [line 736]: Unable to write to or delete from the source due to a data integrity violation. Error Details: Field 'ID' doesn't have a default value

anyone faced the same issue, any suggestions or inputs helpful

thanks in advance