Hood release under the dash has no tension on it. Hood will not latch closed

Normally, the cable snaps off from behind the cabin release lever. In that case you can pull the cable end with Locking Grips. If it has broken at the hood end, and they have a history of it, there are videos in the link to get in through the grill.

https://www.google.com/search?q=2012+Nissan+Murano+hood+won%27t+open+after+pulling+hood+release

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look under the dash see if cable is broken close to that end
grip inner cable with pliers and pull hard

if broken at the engine bay
work from under the car with a long tool to release the bonnet catch

if not sure how its done drive to a panel repair shop for a solution

Check out the cable connection between the latch and your internal latch control. Till you locate the problem I would suggest tying down the hood with some sort of strap so it does not pop open at speed.

The cable is probably broken and not connected to the latch. There are two latches, a primary which the cable is connected, and the secondary or safety.
You'll have to try to access the latch from under the car going up between the bumper and the radiator. You may need a body shop to do it.

lube the hood latch on the car. im sure its dry. lube and work the lube in by closing/opening hood.

You can adjust release on front brace by loosening bolts and setting it. I grease all my latches with moly grease. And lube cable under dash shield.

there should be a lever that is on the bottom edge of dash that is under the steering wheel along the trim. if the handle is broken you can use pliers to grab the cable and pull it to get the hood to realse. if you found all that and i seems to work ok then when pulling the release lever have a friend hit or shake the hood to get it to pop up a little so that you can open it all the way.

go under the dash and cut back the outer sheath around the inner wire cable, then with a pair of vise grip pliers pull the inner cable while someone pushes down on the hood over the latch to lessen the spring tension and ease release

The red release latch is down under the dash on the extreme left hand side. A release tongue should stick out from the radiator grill when the latch is opened. Pulling on this tongue will release the hood When you open the hood the angle is initially restricted to about 45 degrees which is fine for minor jobs. If you need extra room, the left hand hinge has a latch pin which can be swung inwards to allow the hood to move up to about 50 degrees. Releasing the second latch pin on the right hand hinge allows the hood to go vertical. You will have to release the left hand hinge latch pin to close the hood.