What version of TWRP?
I had the same thing happen on my M8 back when I got it in early May. Couldn't get the nandroid to restore, so I ended up just flashing the desired ROM again and setting up the phone manually.
I've since updated TWRP and the restore works (new nandroid). Not sure if it was just a random thing, or a bug with that particular version of TWRP. But updating TWRP is a good place to start.
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Phone: AT&T HTC One (M8)
Tablet: Samsung Galaxy Tab Pro 8.4 (WiFi only)