When I try to log in to my Optimum mobile App I get the following message "Support for this operating system or device model has ended. Please ensure that your device is running Android 5.0 or later." I'm using a Kindle Fire HD (3rd Generation). I'm running the Fire OS 220.127.116.11 on this device. The problem just stated happening today.
NOTE: I do NOT speak for or represent Amazon in any fashion. This is a customer to customer forum.
Disclaimer: I have examined any sites I provide links for and have determined them to be safe but I make no promises about safety, content, ads served or anything that might make you clutch your pearls in horror. Use discretion clicking on links provided by total strangers such as myself.