In case you’re given an old version of a Personal Reserve after the release of Update 1.18.1, it won’t show in the new Personal Reserve activation window. But don’t worry, you’ll be able to activate it from the Depot as usual. Just click on "Depot" in your Garage and choose "Personal Reserves" from a menu on the left. A window will pop up which contains all your Personal Reserves. Hover the cursor over the Personal Reserve you need and press "Activate".
Note: Personal Reserves that come from Referral Program rewards will be the new ones. However, old Personal Reserves may be listed in some materials in the game client and on the game portal.