Access to Unsubscribe button in SRC

Does anyone know what drives access to the Unsubscribe button in SRC Subscriptions? (scrn shot attached)

This is for SRC 1.40

We currently have some contacts that when logging into SRC have that button greyed out for their active subcriptions, but others have it available to select.

All are Individual subscriptions.

Config Mgmt Environment profile has Subscription Request Mode set to Service Catalog.

 

I can not find anything on the operator record that drives access to this functionality. I have two operator records both set as self service users, but one can select the button and the other can not.

 

Any help would be appreciated. Thx.