Synchronizing clips not working

The clips must be labeled in the Inspector before trying to sync them in a multicam clip. For a good tutorial, go to Youtube and search on this (no quotes): How to Edit Multicam Footage in FCP The ULTIMATE Guide

Another trick is if you even roughly know where the sync point is (even within +/- 60 seconds), put a marker on that point of the clip in the Even Browser (M key), before you try creating the multicam. Even though you sync on audio, it will give more attention on the region around the marker point.

To facilitate this, have View>Skimming, View>Clip Skimming and View>Audio Skimming enabled.

If there are some difficult clips or angles that won't sync, you can temporarily omit those when you create the multicam. Once you have the main (non-problematic) angles synced, you can add an angle within the MC and sync specific clips from that angle to a monitoring angle you designate. If it won't successfully sync to one monitoring angle, select another monitoring angle and re-try the sync. See attached.

It could be something with the different clips, or it could be an issue with FCP.

It is worth a try to do what we always do when the application is not working correctly: delete preferences.

To delete preferences, hold down command and option while starting the application and click Delete Custom Settings. The application will start with default settings and open an "Untitled" library. Adjust the settings, reopen the library you were working, and see how it works now.

ALSO: if you are using several video files (e.g. from more than one camera recording the interview) you should make a multicam clip, not a synchronized clip. The latter is meant for one video and multiple audios.

It may work, and at least it is a painless thing to trash FCP and download a new copy; but I would not put much hope in it.

How long are the clips that you are trying to sync? How much free space on your system drive, and media drive?

And how is the drive containing your media formatted?

For a more complete picture: Please run Etrecheck and post its full report here. Use the "additional text" button and paste the report into the text box.

What are the respective frame rates of the two clips? If they are different and if one (or both) of them is a fractional frame rate, have you tried enclosing the clip that doesn't match the project settings in a Compound Clip? Or applying "Automatic Speed" to it? (These two actions force conforming clips to the project settings). An alternative might be to Transcode Media(s) to Optimized. FCP deals better with ProRes.

Please run Etrecheck and post its full report here. Use the "additional text" button and paste the report into the text box.