How much time have you been minting these coins? It is enough UTC to mint more than 0.00, so maybe its time what is needed here. Let them rest at least two weeks to one month. As I understand, it takes 7 days for the coins to mature and be ready for minting.

Also, check that your coins are all in one group. Many times the coins are in the same address but are organized in different groups. If a group of coins is too small (5-10 UTC), and that group is minted, it also gives 0.00 UTC. (Check the send coins tab for viewing group coins in the Group Coins button).

Hope this helps.