There are some possibilities here for waht's wrong.
First, if the file wasn't properl;y closed there may still be a lock file (.idlk) in the same folder as the .indd file and you should delete it.
Second, if this is a file from a previous version or another user on another system, there really might be a missing plugin.
Third, it's not really an InDesign file at all, but something else that the extension has been changed on.
Fourth, this is a synch file for a cloud-stored file. If that's the case you can probably download the file to your system first, then open it locally.