Sorry for the late reply!!! Log out of the Facebook account on your phone. Make sure you have the amount of gems you want on the mod. Then, log back into the Facebook account on your phone. It’ll ask you if you want the new or old data (something along the lines of that, I forgot). Make sure you use the new data (the gems that were added). It should work then. If not, let me know and I’ll just send you a video of myself doing it.
By the way, I don’t know if your “spent and got 10,000 gems” means that you got the 10k gems and *then* spent some of it— just making sure, because that’s the way I did it. I don’t know if doing it in the opposite way works.