I had this problem once, ended up being the front panel being little lose. Once I pushed it in, it stopped the problem. Try nudging them in if you see a gap, one of the clips could be off/loose.

 

This is a pretty common problem. I have it on my XC70 from time to time. When it happens I hit the latch with some WD40 to loosen things up a little. I don't recall if it's the driver side or passenger side that has the sensor on it. If it continues you can either replace the latch assembly or put a jumper wire in the electrical connection for the sensor and while you won't have that sensor working anymore at that point at least you won't get an annoying warning.

 

The problem with this is it can also set your alarm off if you have the car locked (which is what happened to me after a while). The fix is replacing the latch if you still want to sensor.

I think it’s pretty unnecessary. I did what was mentioned above: disconnect the sensor wire and I simply used a paper clip to jump the connection and taped it up with electrical tape. Easy fix.

 

The fix can also be as simple as leveling the hood. There are two rubber bumpers on each side of the engine compartment. They can be raised or lowered by simply turning them. Adjust them to make sure the hood is snug when closed..

 

Older thread, but thank you so much for this suggestion! I have a trip planned in 2 days and could not get into the dealer (it takes weeks for an appointment nowadays). This seems to have fixed the "hood open" problem on our 2016 XC90. I raised them up and the message has gone away!
Thank you!

 

Good to hear!

 

Glad you found your fix. I have to go out and try raising up the rubber bumpers and hope it does the trick. Last time I got the message I was able to fix it for a few months by blasting the latch assemblies and exposed bit of rusty cable with penetrating oil because it seemed at least one of the latches was sticking a bit. It didn’t work this time around.