In order to permanently lock models, the following requirements must be met.
General
Locked models must be closed.
Function privilege
You have the Lock permanently function privilege or are a system user.
Access privilege
You must have the Write access privilege for the model you want to lock.
You must have at least the Read access privilege for all object definitions of the objects used in the model.
Method requirements
Every object occurrence must be allowed by the method filter in use.