Trouble sharing Macs on same network

[tuqqer]

Thank you, Sarcany.

Weird, we're able to connect one of the 4 Macs in the house via your tip, but the main one (my wife's) accepts the password but then immediately says Connection failed in the upper left (instead of Connected as...) when it works. Both of us are on Catalina

So far we've tried deleting the User account and creating anew, rebuilding permissions a few times, restarting, and multi-verifying the password. We'll try again tomorrow.