Modem Shows Connected but none of my devices (wireless and ethernet) remain connected

I have tried Cox support multiple times and am always just told to buy new equipment.

Anyways, I have an Arris modem that was purchased less than 2 years ago when I moved to my current house. My modem will show all blue lights which tells me that my internet should be connected, however, all my devices will disconnect despite the fact that they show I have full strength internet. The follow devices are what I typically have connected (they all lose connection when this happens):

TCL Smart TV (ethernet connected)

iPhone X (wireless connected)

MacBook Air (I switch between wifi and ethernet based on where I am in my house)

It feels like I have to reset both my modem and router (just the modem doesn't seem to work) multiple times a week lately. Typically I would just do the reset and get on with my life, however, I do online ESL tutoring a few times a week and have been disconnected from the students and I'm now in fear that this job will soon be in jeopardy because these families pay a lot of money to be tutored by someone who keeps getting disconnected.

The only solution Cox had was to buy a new router. Any thoughts? Things work fine for a time after resetting my modem and router, but it's a huge inconvenience and could cost me some needed income.

Thanks in advance.