Syncing Issues in Premiere Pro

Hi!

I'm working on a short film for uni in Premiere Pro 2023 on a Macbook Pro with 64GB Ram, Apple M1 Max Chip, on Venture 13.3.1 (a). 

The shortfilm footage is 1920*1080 at 25FPS in the XAVC-I Codec, shot an a Sony FS7.
I don't know the details of the audio equipment, however.

We did not get timecode.

I need to synchronise audio with a boom, however the audio synchronise option gives an error message that reads "Could not synchronise one or more clips in the current selection because a match could not be found".

After researching the issue I found that apparently changing the trackchannel option in the synchronise settings to "Mixdown" solves this. However no such option appears for me.

So, I tried syncing manually but the audio from the boom has no waveform, making it really annoying to sync, the only way I could find to solve this was the "Render and Replace" option, however according to the post-sound team, this causes issues for them.

Does anyone know how I can either safely get a waveform to appear in a way that wont effect the post sound team, or a way to get audio synchronise to work?

Thanks!