Re#run the ‘update music library’ process? Which may need to include resetting the ‘here is where all the music is stored’ definition in the Sonos controller. 

And possibly, it may just be that deleting the app from your PC, and then doing a re-install may be enough to ‘reset’ the file location, since the library is local, and not on an NAS. Just make sure you ‘join an existing system’ if you do that, as your speakers are actually where most of that exists. If you ‘create a new system’, you’re essentially wiping out everything previously set up. 

On many levels you can think of the SONOS controllers as a simple remote control, very little is stored in a controller. The SONOS players manage the minute to minute system operation details. When you renamed your PC, as far as the players are concerned, you moved the library to another location. Sometimes the players might figure out a rename, but this is not guaranteed. Using a SONOS controller, go to Music Library Settings, delete your old library, and setup a new library with the new location. This will not modify your files in any way, it simply points SONOS to the correct share.

You may have some trouble with SONOS Playlists. I don’t know if they will be aware of the move.

Solution for me was as simple as add new location and remove old location.

I saw that old location was a local network path so held the wrong pathname after the computer name change.

Thank you @buzz .