Hi,
After a reboot, I notice that witeguard does t work. It shows as enabled, but so need to disable it and enable again for it to start working again. I have tested this three times, and it seems that somehow it always shows as enabled after a reboot, but si have to manually disable it and enable again.
Probably, the DNS is not fast enough to let you access the other side. Also, Wireguard never queries DNS after initial connection buildup.
There is a cron job "Renew DNS for WireGuard on stale connections" to take care of such situations - if the connection is down, it just restarts Wireguard.