In order to be able to access any database in LN you have to be a ” Full Access Administrator” turn this on to over write the Domino ACL and then do the following :
1- right click the desired database
2- click the ACL ( Access Control List )
3- Add your name over there as a person and a manager .
This will add you as a specific user to the ACL…. or you could add the Administrators person group as this will cover any other admin in your organisation.
Hopefully this is Helpful