Ugh, that's so frustrating. I had a tile guy vanish after a bad job. I ended up filing a complaint with our state's contractor license board. They actually reached out to him on my behalf and it got things moving. Check if your installer has a license and go that route. It took some time but it was the only thing that worked.
Check their Facebook marketplace or Nextdoor listings - some of these guys flip jobs super fast and might be advertising new work while ignoring yours. If they're posting fresh projects for other people, screenshot everything and use it as proof they're actively dodging you. That kind of public evidence usually makes them jump when you finally file that complaint.