Had this same issue a week ago, when card 4 of 6 would not change...

   I ended up doing this:

  1. running atikmdag patcher to put the drivers back to normal
  2. go into Control Panel\Program and Features, and uninstalling the AMD software
  3. running the AMD clean uninstall utility
  4. reinstalling AMD 18.2.1
  5. running atikmdag patcher to patch the driver signatures

  I was then able to get all 6 cards to change to Compute -