So many things that could cause Euphyllia to not expand. Water quality, too much/not enough light, physical irritation, too much flow... You need to look at each of these.
Two things that I see from the pics... 1, make sure it's not in contact with the rock next to it. Looks close to me but that could just be the angle of the photos. 2, I see you have a clown. Many times they will try to host Euphyllia which could irritate the coral at first. Or other things like crabs could irritate it. Usually these aren't doing any damage, it's just annoying and the coral eventually gets used to it if it's otherwise healthy.
Having your water parameters in check and good lighting along with decent flow are the other immediate items I would focus on.
And it could just be this particular coral. I've had some torches that just didn't do well, must not have been very healthy to begin with, while others grew like gangbusters. Getting another torch frag from a completely different source, one that looks healthy to begin with, could be a good test.