Captains,
Very first things to do when you experience any issues with the 777/767 for FS2020:
1. Make sure the Asobo 747 is installed.
2. Remove all third party mods.
3. Re-install the 777/767.
4. Do not use any flights saved with previous versions of the sim and/or the 777/767.
5. Search the forum. Most issues are discussed\addressed already.
6. Found nothing similar? Post it! But do not expect a reply if you just skipped the step #5.