@mbarbaro 

Hi,

When you lose internet, will the devices still connect to the router's WIFi?

Please insert the SIM card into another router and test if the SIM card can get stable internet access. Or you can insert it into a phone and enable a hotspot to test,

And you can also check if there is a new firmware for the router. And check if the firmware update can help.

And about the DDNS issue, please maker sure that the router can get a public WAN IP.

Troubleshooting Guide of DDNS function on TP-Link Wi-Fi Router, LTE Gateway Router or Deco Router

If all steps above cannot help, please contact the support directly with results above.

Contact