After a recent “update”, the MFDs are either missing, in the case of the Cessna CJ4, or distorted in the case of the F-15. (Other aircraft could be effected, but these are two that I regularly fly.) [MSFS 2020--Upgraded MFD follies]

In the case of the CJ4, make sure that you’ve removed the old WT CJ4 mod. Having that installed can cause displays not to work. No idea what’s up with your F-15 though.