I'm on version 126.96.36.199 and stuck on "Checking for Update". Can someone direct me to the firmware files for my device so i can update the firmware manually?
That is not possible. Hubitat does not allow downloads of firmware to something like a desktop or laptop. The hub must do the update.
The most common cause of your issue is a lack of communication from the hub to Hubitat servers. Your internet is either misconfigured on the Hubitat hub, or maybe you have something like a Pi-hole or other firewall blocking access.
Did you by chance set a Static IP on the hub? That is very easy to misconfigure and will cause the issue you are having. Change back to DHCP and see if that makes a difference. You can also do a network reset on the hub by following the reset instructions in the middle of this page Network Setup | Hubitat Documentation.
Sometimes you are able to get past this by using the diagnostic tool "Download Latest Version" button and then "Restore Previous Version" which actually lets you update as well so the button name is misleading.
Not sure if this endpoint will work on your firmware or not, but you may also want to make sure you have an updated diagnostic tool as well. Explained here: New Diagnostic Tool Version 1.0.97