Specific class of routers being blocked

Ever since some ‘scheduled maintenance‘ last week my SOHO router no longer works with the modem. Modem has been swapped out as well. I’ve tried another brand of SOHO router, same thing. Two different consumer routers work and if I double NAT while forwarding all traffic to the SOHO router, it works fine. Spectrum is blocking traffic on the two SOHO routers. Is this intentional and if not, how do I get past the unskilled tech agents on the phone to reach someone who can do something about it? DNS traffic is getting through, but anything else is being blocked, unless I put a consumer router in front of the SOHO router. The SOHO was fine for 2 years before these recent system changes. This is either a policy or a misconfiguration on Spectrums part and it's impossible to get anyone with actual knowledge to do anything about it. I now have 2 routers in series, which I don't want to do indefinitely.