Mac works fine on local wifi but won't connect to internet
I was happily helping a friend with her web site when my MBP crashed and restarted. When it came back up, I was connected via wifi to my LAN. I could see devices, mount local servers, ping my router, etc.
But, I could not get outside of the network. Via USB cable, I tried using my iPhone's personal hotspot using both its LAN connection and mobile service. So, there's no problem between it and my router.
All the other devices on my LAN work fine. Any suggestions? It's running Mojave 10.14.16
The only easy thing I can think of doing is upgrading to Big Sur and hope that repairs whatever the problem is. Of course, that will kill some software that I use. I would like to avoid that on a speculation so I'm hoping someone out there has a fix.
Thanks!
MacBook Pro Retina