Hi painterman,
Welcome to the forum. Make a cup of coffee! You are almost there hopefully.
Does the pvr work ok without hard drive attached? If it does, then I would guess that the hard drive either has a fault preventing it booting correctly or something else going on.
If you have already purchased hard drive, it’s very easy to fit & the Humax should work ok with it once fitted. You just go into the settings and format the drive. It’s then ready for recording. John L