Setup was unable to determine if "MMAccessKey.ini" exist on the machine with the Deployment Share. Cancelling setup.
Reinstalled PXE on a Deployment Solution 6.5 server and when attempting to start the PXE Manager the same error message is received.
Deployment Solution 6.x
MMAccessKey.ini is corrupt.
This can also happen if you are installing DS and there is another share on any of the other drives shared out as "express"
Try to re-create MMAccessKey.ini by following suggestions of article PXE Key Match Utility and, if re-creating the MMAccessKey.ini doesn't help with the issue, the next step is to perform a fresh install of Deployment Solution.
Note: Before doing a fresh install of Deployment Solution, make sure you back up your images, packages, and jobs that way they can be used on the new install server.