@bradmoss 

The support team is spot on. TP-Link’s built-in DDNS (tplinkdns.com) is notoriously aggressive with its caching and frequently drops or throws SERVFAIL errors when queried by third-party services like Control D. When Control D hits that wall, it assumes your IP no longer exists and drops the profile link.
Since you don't have a 24/7 local device (like a Raspberry Pi or a PC) to run Control D's daemon or a heartbeat script, you need to hand over the DDNS duties to a provider that your Archer AXE75 natively supports and that behaves nicely with Control D.
Here is the exact play-by-step to fix this:
 

Configure Your Archer AXE75

1. Log into your router’s web interface (192.168.0.1 or tplinkmodem.net).
2. Go to Advanced > Network > Dynamic DNS.
3. Change the Service Provider from TP-Link to No-IP (or your alternative choice).
4. Enter your new hostname, username, and password.
5. Click Save and verify the status says Success or Connected.

3. Update Control D

1. Log into your Control D Dashboard.
2. Go to your Devices tab and select your router profile.
3. Replace your old xxxx.tplinkdns.com address with your new myhome.ddns.net hostname in the IP tracking/DDNS section.

Once this is linked, Control D will check the No-IP hostname instead. Because No-IP doesn't intermittently drop off the map with SERVFAIL responses, your Control D profile will stay active and locked to your dynamic IP.