Unable to connect to remote servers, premium streams

This seems to be a reoccurring problem. For some reason our panoramic gigablast router isn't allowing us to connect to certain remote servers. We can watch Netflix and Hulu on the TVs (Firecube, Firestick) but can't connect to Disney+, Prime and other premium streams. Also have problems on our phones connecting to games. First time this happened we had intermittent internet for 3 weeks. Second time, issue resolved itself after a few days. This time it's been 5 days. Router has been replaced twice; tier II tech came out last time and couldn't figure out the cause, but thought that maybe the Cox wifi app was breaking the router. Router has been restarted numerous times (since that's all that Cox knows how to troubleshoot with). Getting tired of this.