SAP Message SMOE_MESSAGE820 - Site &1 has own subscriptions. Assigning a Copy relationship not allowed

Diagnosis
You are trying to assign a parent site to a site having its ownsubscriptions.
This is not allowed because dependent sites cannot have subscriptionsof their own.

Procedure
Deassign the subscriptions from your site and save the changes.Afterwards you can assign a parent site to your site.