OK. I don't know if it hurt anything, but 12.5g is a lot of Go-Ferm for 5g of yeast. You only need 1.25g per 1g of yeast.
I just realized you stated you used 18 lbs of honey. Not sure if you verified the weight, or just went with a rough measurement based on volume or what any packaging stated, but that does seem like a really high SG for that much honey in a 5 gallon batch. I'd almost want to get another hydrometer to test it with.
I don't know when you pitched it, but if there is no evidence of fermentation, then the yeast are likely struggling. As Squatchy mentioned, atemperation is important if you do pitch more yeast, so you'll want to get your must to the right point first. The Scott Labs 2019 handbook has good instructions on rehydrating if you want to google that (the handbook is free).
Assuming no fermentation activity, and a true SG of 1.5 (if hydrometer is good), then I'd start with diluting the must. That may get your yeast going, and you can pitch again if it doesn't. It might not be a bad thing to pitch more just to make sure, but be sure to follow the rehydration protocols. If you do get it down to 1.129, and it ferments to 14% ABV (D47's normal tolerance), you're going to have something around the range of 1.020, which is in the dessert sweetness category according to my understanding.
Others may have more/better input, but those are my thoughts.