I had a similar issue.
While migrating DHCP servers around, the Route10 ended up disconnected.
ssh into the route 10 and I couldn’t ping anything as it had lost dns settings in the DHCP changes.
So a work around I added google dns (8.8.8.8) to the bottom of the resolv.conf file
nano /etc/resolv.conf
contents then look like this for me
search localdomain,192.168.2.1/24 localdomain,10.10.10.1/16 localdomain,172.16.5.1/24
nameserver 127.0.0.1
nameserver ::1
nameserver 8.8.8.8
That let the route10 reconnect to the cloud controller, and resync the updates to the DHCP server settings, and reset the file removing the addition above.