Upgrade from 21.1.7 to 21.7.5 not posivle

[matzeeg3]

hi everybody,
i have trouble with one of my opnsese system. it runs in a virtual maschin and at the moment it runs 21.1.7.
i like to upgrade to 21.7.5 but the system reports not update.
i try to change the channel and every thing else but it did not work. even from the cli not working.
what i have to provide that you can assist with it?
Kind regards