Most IOT devices no longer connect to my 2.4ghz guest network. What's going on? (SOLVED)

FINAL UPDATE W/ SOLUTION: It hadn’t dawned on me that my wifi extender could have been creating issues, until I realized that it was only pushing my guest SSID to devices at the far end of my home and outside. I literally unplugged it and all my IOT devices connected and have stayed connected! So, not a router issue, but the...