Diagnosis
This occurs when the firmware file you are attempting to upload is not intended for the RAXE500 model, is corrupted, or is an older version than what is currently installed.
How to Fix It
Do not use manual firmware upload. Instead, use the router's built-in update check. Log into routerlogin.net. Go to Advanced > Administration > Firmware Update. Click 'Check' next to 'Online Firmware Update'. The router will fetch the correct, official firmware directly from Netgear's servers. Follow the prompts to install.
If That Didn't Work
If the online check fails, download the firmware manually from the Netgear support site for the RAXE500. Double-check the model number. After downloading, go back to the Firmware Update page, select 'Browse', and point to the downloaded .img or .chk file. Do not unzip it.
Heads Up
Never interrupt a firmware update. The router's ring light will typically pulse white and amber during the process. A power loss during this time can permanently brick the router.