When you go to FTMO app you will notice that AUDUSD only had 2 trades last week and the other 2 top robots only had 1 trade. So as you can see the robots do not trade very often. For this reason you need to give the robots more time to open trades.
As for the 50k and 10k challenges did you download and install the 50K and 10K robots? If so then I think you just need to give the robots more time to open trades.