Persistent internet issues after outage, only some devices connect

I'm having a critical internet problem after a long outage last night in my area. Since the service was restored, my connection has been severely unstable.

Only some devices in my home can connect.

My computer, phones, and Harbor baby monitor camera are all unable to connect. This means we cannot monitor our baby, which is very concerning.

I've already spent hours troubleshooting with three different customer service representatives over the phone.

We've gone through all the standard steps (power cycling, checking cables, resetting the modem), but nothing has fixed the problem.

I work from home and need reliable internet for emergencies and on-call situations. I cannot be without connectivity.