Hi, curious if anyone on here sells flights from their points on a bigger scale..? Looking to network with people and gain more knowledge on this

Has it happened to any of you? My partner got 2 amex gold card, she spent 10-11k on each of them around Jan, then she paid off. But this month, on one of the card, seems like limit is about 2300, and another we tried to spent 5k and that got declined as well. Any idea why that happened and whats the solution to increase the limit back again?