As you mentioned, the Access Point that is not working is PWR red, so this means the unit is stuck Boot up in process, please follow up the next steps:
1:Reboot the unit by disconnecting the Ethernet cable from the Switch, wait at lease one minute to reconnect it back in.(if the issue persists move to steps#1)
2:Move the working Access Point to the no working Access Point port, so we can discard is the issue is the port in the Switch. (if the working Access Point works fine on both port, move to the steps#3)
Note: the yellow ports are the Ethernet ports where the Access Point must be connected to the Switch.
3:Remove the Access Point from the ceiling and or if you can do it from the same ceiling great, and perform a factory reset let me add the guide to perform this step, please provide the results.
Physical Factory Reset Access Points Ruckus
Note: The passwords I have shared, is to access the Unleashed application.
Technical Support Engineer | L2 TAC Wired