My dog is about 1.5 yrs old he's not neutered yet but today we noticed that both his testicles have gone back up to where his penis is, as in they are not in the scrotum sack anymore. Is this normal? Do we have to massage them down again?

What you are seeing is most likely not the testicles.

How to put this delicately... when a male dog gets excited (especially when entire) their glans swell up near the base of the penis which will look like 2 lumps. That is normal and the swelling will go down in around half an hour once the dog calms down.

As for the testicles apparently being missing this is definitely not normal and needs to be seen to by your vet. Do not massage them, testicles do not suddenly retract at a year and a half of age for no reason.
Were the testes normal until recently? How long have they been 'missing' for?