Hatch won't open even with manual lever from inside

2007 Prius, about 130,000 miles.
The hatch has been working intermittently for a a month or more, where it doesn't open right away, have to keep trying.
Yesterday the car wouldn't start and suspected the battery. Gave it a jump and it started right up.
Got a new battery and trying to install it, but the hatch won't open.
Climbed into the back to pull the mechanical lever, but still doesn't open.
Pulling the lever causes something to release and the door starts to open a tiny bit, but there is still something else stopping it. It feels like there is a secondary latch or something that is still interfering.
Any ideas??

Joe

 

We were able to get the hatch to open. Previously the key was in the dash while trying to open it with the mechanical lever. This time I took the key out and had it with me when opening the hatch. I still needed someone pushing the mechanical lever from inside. But it just opened. What ever mechanism was preventing it from opening (after pushing the lever) it is very quiet. Nothing appears to change but magically the hatch opens. ?