missing from my wifi list

I have always had both a 2.4GHz and a 5GHz Home Network wifi access with same username and password for both. I could switch between them whenever. But for the past 2+ weeks my 5GHz has not be showing up in my list of active wifi. Did something change? How do I get it back. I had to reset all my devices to 2.4 that didn't toggle automatically. Now my network is so slow. Can someone help or at least explain what happened? Thank you in advance