If you are having any of these issues, please read below. I had all three.
If you are receiving the 502 bad gateway message and unable to reach the router GUI at 192.168.1.1, you have to flash the firmware. A factory reset will not get you back in to the router. The only way I could accomplish this was to use TFTP program http://tftpd32.jounin.net/tftpd32_download.html. Again, a factory reset is not going to get you back in. You must flash the firmware.
Follow the instructions posted here the for a Netgear firmware flash.
https://kb.netgear.com/000059633/How-to-upload-firmware-to-a-NETGEAR-router-using-TFTP-client
The key is to "PUT" the bin file onto the router while it is booting. It is different for the Cisco router, so read this on how to get it into the boot loader phase.
https://www.paladin.technology/tech/73-cisco-rv325-firmware-update-via-tftp.html
Make sure the server interface is set to the static IP you set earlier and not another IP. The PWR LED should be blinking green and the DIAG will be solid red. Click on PUT and you should see the status bar filling up. Voila!
Now if the certificate is bad, like mine was, you can fix that too! You should be able to log in to the GUI at 192.168.1.1 using cisco/cisco. Under System Management, there is a Factory Default option. There you can reset the router to Factory Default including Certificates. That will restore the router and remove any certificate issues.
Hope this helps. It took me 2 days to track this method down and lots of help from this forum and the web. Let me know if this solution worked for you.
John
