But this is not a DDNS issue.
DDNS will resolve the hostname to the last known public IP. If the public IP isn’t changing, we have no DDNS issue here.
To check ddns, please use a name resolve tool, like nslookup or dig.
nslookup [blank].glddns.com 8.8.8.8
should always point to [blank].8 in your screenshot. The 8.8.8.8 is the DNS server and optional for our test.
The fail in your screenshot is ping, not DDNS!
Now we have ruled this out, and going to ping.
Ping is sending an ICMP package. ICMP is good to test if a host is available. But when it comes to the internet, many people have the opinion ICMP is the pure evil, every hacker in the world can hack you, just by ping your host … So they engineered the ‘stealth mode’.
I’ve seen ICMP blocks from LAN to WAN in corporate networks … It exists, believe me.
You are saying you are using a travel router. So I assume you are traveling and switching networks.
I suggest to use iperf3 as solution in this case: iPerf3 for beginners
Of course every other TCP or UDP service will work as well, but please don’t open a http server on your router, exposed to the internet! there are bad people out there, which know the banner of embedded http services and what to do with it.
Install the iperf3 client on your client computer. And I’ll say this will work, even if the WG does not. Maybe because between 7:30am and 3pm anything in your remote LAN is blocking WG.