Can't connect to Walmart in-store WiFi with LTE ZTE Maven Z812
This appears to be an interesting but known issue with 2.4Ghz only capable phones. Here is an article that explains the issue and why it is happening. If that doesn't work or you don't trust the url, just do a quick search on Android Central Forums for "why does my phone disable wi-fi connections" and it should be the top result there.

https://forums.androidcentral.com/ask-question/865480-why-does-my-phone-disable-wi-fi-connections.html

I recommend going to your Wi-Fi settings, possibly advanced settings, and disable smart network switching. It might be "Switch to mobile data" or something else like that. Once you have that disabled forget the SSID and then try to connect again and see if it works for you. Hope that helps!