Sadly not, you need to be on OOS 11.
Presumably the MSM reinstated a version of 11?
There’s probably a couple of ways to proceed. You can downgrade to 11 on device by grabbing appropriate packages from XDA thread which I’ll find in a moment. You will need an apk for system updater app so that you can do local downgrade/upgrades etc (I believe it’s missing in OOS 12)
Or you could msm again back to the OOS 11 build (what version is it btw?) and then do a local update to the latest/last 11 build which is 11.2.10.10
https://forum.xda-developers.com/t/oneplus-9-pro-rom-ota-oxygen-os-repo-of-oxygen-os-builds.4254587/