My HI8 was not seing channels above 11, also when trying to reinstall a new driver, the wifi got broken.
The fix is to modify (create it incase is missing) a file in c:\windows\system32\drivers called 43430r1nvram.txt.
In that file the field ccode=ALL must be replaced for ccode=JP. Then the tablet can see channels above 11 (12,13,14)
The extension of the file should’nt be modified/removed.
Hope it helps