Referencing this post/solution:

https://community.tp-link.com/en/business/forum/topic/264462?replyId=598036 

I am experiencing similar issues since soft resetting my ISP provided router.

A bit of infrastructure info:

I have an ER605, OC200, some tp-link switches and some tp-link APs connected downstream from my ISPs gear on a DMZ. Everything has worked as they should for years. Recently did a soft reset of the ISP router and started having the issues above.

I am still connected to the internet and everything works as it should except for me being able to access the controller to administer anything.

I have spoken with my ISP who cannot/will not provide a private IPV4 address.

Are there any other potential solutions or could it be that me controller has decided to pack up?