What to do when an older Adobe app will not open a newer project
This error usually means the file is not broken; the installed app is too old for the project structure. Either upgrade the app that opens it, or bring the project down to what that app can read.
Confirm it is a version mismatch
If the message says the project was created in a newer version, or it fails immediately with a version warning, treat it as compatibility. First identify whether the file is Premiere or After Effects.
Upgrade first when that is possible
If the recipient can upgrade, that keeps the most information. Downgrading exists for delivery constraints where the receiving environment cannot move.
Downgrade when upgrading is blocked
Choose the target version the recipient can open and generate a new older project. Downgrading removes what the old version cannot support, so choose the closest target that works.
A version error is not the same as missing media
Compatibility happens at the project-file level. After downgrading, you may still need to relink footage; that is a separate delivery check.