Syncthing tries to use UPnP to create automatic port forwardings, aiding in establishing better/faster connections.
This error means that something in the UPnP query has gone wrong, probably because the router in question does not support/allow automatic port forwardings.
Syncthing can usually work just fine without UPnP, so this should be no big issue.
Thanks, folks, that is comforting.
I recently upgraded routers to RT-AX86Us from AC86u’s and my modem also.
That may possibly be the cause.
thanks again,
jts