Issuing a TSS REFRESH command after making DB2 security changes to an ACID in CA Top Secret is not taking effect. The ACID signing off and back on doesn't help either. The DB2 address space has to be recycled for the changes to take effect.
DB2 has the ability to cache security checks for performance purposes. Since it's a DB2 cache, the TSS REFRESH command cannot refresh it.
You will need to disable DB2 caching if you wish to use the TSS REFRESH command to dynamically pickup security changes in the DB2 address space.
Another option would be to flush the DB2 cache after making the security changes. Use this option if you wish to continue using DB2 caching.