You should have continued on in the topic you recently created instead of starting a new one.
There are some resources in the following topic, which also indicates that the company is out of business so the sources for a replacement mainboard might be limited to Amazon or eBay, but as always I would look into whether the circuit can be traced and a discreet component fault on the board found... which can often cost only $10 or so for a component instead of $$$ for a circuit board.
However I can imagine it could be hard to share with us all the various wiring and motors in pictures to try to reverse engineer this remotely so if you can't DIY, and if you can't find a board either, the next best step would probably be to hunt down an electronics repair shop in your area, something ran by an old timer that has been repairing TVs/stereos/etc for decades (not a commercial chain Best Buy geek squad/etc service center), then you hope they don't mind you dragging a chair to them since it's going to be larger than what they're used to dealing with.
https://www.electronicspoint.com/th...-products-php-2026-2027-massage-chair.283587/