Thank you! This was exactly the hint I needed. Although I had turned-off and disabled by VPN (ExpressVPN) before trying to start Private Relay, I had not deleted/removed the application from my MacBook Pro. Once did totally delete the application, the toggle to turn off Private Relay appeared and was accessible. I was finally able to turn it off and get my machine back.
I have elected not to use Private Relay on my MacBook as I use if for work in addition to personal use. My employer requires I have a VPN installed so I can't use Private Relay if it is incompatible with my VPN. Once I got Private Relay turned off, I reinstalled my VPN and reenabled it. I won't be turning Private Relay on.
I will note that I was able to start Private Relay on my iPad Pro - 4th Generation (iPadOS Version 16.2) with the VPN installed but not enabled. Living dangerously, I reenabled my VPN once Private Relay was turned on and they have been coexisting problem-free for about a month, now. No known or observed issues.