I recently was looking at a 2 night stay for 18k points each night. Since I have a free night certificate and it is now a category 4 property I wanted to do a mix of paying one night on points and one night with the certificate, since the certificate should work for a standard night. I called the Globalist line to make the booking since the UI did not give me the option to use my free night certificate for one of the nights. After transferring me around a bunch I was ultimately told that I couldn't use my free night certificate for this. It's quite disappointing, the free night certificates feel useless if I can't even use them at Cat 4 properties with standard night availability.