I have a 502 that is out of upgrade date and I tryed to upgrade but it wont take. Am I wrong about the upgrades. I thought if you had a 2.9.x it would be upgradable to the latest version of 2.9.x.
Update :I did an upgrade to 2.9.35 and it took just fine. The first failed upgrade was was with 2.9.43 all in one package via winbox. The second was 2.9.35 all packages via FTP. Now I have upgraded to 2.9.43 all in one package via FTP and it’s working fine.
It’s all good for now! 
For future reference, you can download the updated firmware to your PC desktop.
Next open a WinBox connection to the device and open “files”, reduce the size of the WinBox GUI exposing your desktop.
Now just grab the updated firmware from your desktop and drag it directly into “files” (outside of any folders within files) then issue the reboot command.
Once the unit reboots it will have installed and incremented the firmware value.
Thats what I did the firt time. I almost always do it that way. But, I doesn’t work untill you set an IP and connect to the IP. It doesn’t work if you winbox to the mac address.
Just did 30 yesterday with mac. Just don’t use secure mode.
LOL, yep! That would do it. 