UTAU Synth for Mac is not really worth it. You should go ahead and try OpenUTAU, otherwise you're in for a lot of trouble.
If you really want to try, make sure it's the correct version. Ameya just posted a beta version to their Twitter that works for the current version of MacOS. It was a couple weeks ago. This is the reason your program won't work. It's not compatible with Mac M chips, as well as newer operating systems. The Twitter release is, and should work fine.
Next, DanteDesigns guy has a really nice patch with quality of life improvements.
https://dantedesigns.net/nib.html
Lastly, some Voicebanks will crash the program. This is trial and error, as I'm not sure what causes the VBs to crash. It's rare, though. And Bluetooth output can also crash the program, or silence your computers sound for the next hour. (Or until you restart the computer.)
OpenUTAU on them other hand has a learning curve, but it does pay off in the long run. It's a worthwhile upgrade. I wish you luck, whichever program you use!