Not Enough Currency
It says not enough currency but I have plenty of XXX, why?
The currency needs to be residing in your account not your inventory. Pick which market you wish to make a deposit in (meaning, which currency you are depositing) and then click "Deposit" at the top of that market window. Whatever currency amount you have in that account is what you use for spending.
Note: This is only for physical currencies and is not necessary for RP