Symptoms:
When you try to run the PreUpgradeCheck command, you get the following message:
Pre-upgrade check cannot proceed because the current farm is not joined to a farm, or the farm configuration database is not responding.
Cause:
Probably you don't have the sufficient privileges to run this command.
Resolution:
Run the command prompt using Farm Administrator account or alternatively "Update farm administrator's group" through Central Administration page, by adding the current logged on user.