Read the instructions in this article:

https://support.sonos.com/en-us/article/connect-sonos-to-a-new-router-or-wi-fi-network
 

If you have the ability to change the network name and password of the new network to the same name and password as the old network, this might work too.

I’ve read that many times but it doesn’t come close to resolving the issue and is incomplete. I was able to find another page to suggest to reboot my router. I did that and it got me to the point that I could put in my network (which I had to manually enter) and password. When it tries to connect it errors out without any further instructions or troubleshooting. 

Have you tried to change the network name and password of the new network to the same name and password as the old network?

You could temporarily connect a Sonos device (not a surround or Sub) by cable to your router and see if you can input the right credentials then.

Does your network comply to the Sonos network requirements mentioned here: https://support.sonos.com/en-au/article/sonos-system-requirements