The difference in code from 9.8 to 10.2 would be causing the image failure. You would need to convert the AP image to standalone and then it should accept the 10.2 image.
1) Perform a f/d on this AP by CLI or physical reset button.
rkscli: set factory
On the AP back console using paper clip, press hold the button which says "Hard Reset" within a tiny circular port for about 10 to 12 seconds.
2) Download below image :
3) Upgrade using CLI or WEB :
Note : For 10.5.x you will need to make sure HTTPS is enabled between AP and ZD since from this code AP takes image upgrade using same port (security enhancement) or alternatively you can enable legacy mode by enabling FTP for upgrade and can disable it later.