Check your AV Vault/Chest to see if anything from the Captain Sim 767 has been flagged as a virus/trojan and been move there. If you find anything, restore it/them and add it/them to the "exclusions" list so your AV doesn't remove them again.

If you don't find any files in your AV Vault/Chest, the reinstall it. Make sure your AV is off/disabled, then right click on the installer and select "Run as administrator".
See here for reinstall instructions: https://www.captainsim.org/forum/csf.pl?num=1554738484
Before turning on/enabling your AV, run P3D and see if it works. If it works, then after the AV has been turn back on/enabled, and the problem P3D crashes the next time, then the first thing I said, is most likely the reason.


Note. Captain Sim products do not include viruses/trojans, but often some files will get a False Possitive, and be removed by the AV.