Won’t stay connected to 5G network.

My fiancé and I are having issues connecting to our new 5G network. She has an iPhone X and I have the iPhone 11 Pro. We have century link fiber internet and have had technicians in and out but our iPhones still won’t stay connected to our WiFi.

We have reoccurring prompts that say either “incorrect password” or “unable to connect to network.” So for I have: restarted my iPhone; restarted the router; reset my network settings; forgotten my WiFi network and attempted to rejoin, and nothing has worked so far. The annoying this is that after we had a century link technician in last week, our WiFi was working fine on our phones. Now it’s not working. The technician has no clue what else to do. So we need some assistance. Any thoughts?