ORBI RBS50 stopped connecting and cannot get it to connect back to router

Did you restart the RBR50 (router)?

When the satellite turns magenta, that means that the satellite thinks it is working, but it is not getting an IP address from the router.

https://kb.netgear.com/31018/How-do-I-sync-my-Orbi-router-and-satellite 

You might try saving the configuration file to your computer, doing  a "factory reset" on the router, and then reloading the configuration file.

(because it is such a chore to do a complete setup)

If loading the config file also fails, then the last step is a factory reset and complete setup on the router.

Even if you order a completely new system from Amazon today, you will be without a satellite for 24-48 hours, which leaves plenty of time to fool around.

Needing a new satellite does raise the question of (a) sinking more money into a technology that is "gradually becomming obsolete" or (b) taking the plunge and investing in the newest technology.  If you need coverage now, getting WiFi6 means picking a completely new product.  The Orbi WiFi 6 is not scheduled to ship until the end of October.

Sorry I don't have any quick solutions.