Since you found a block it means it’s working. Unless you changed anything from the Bitcoin mining specs, the mining block target is 10 minutes.

Which means the average over a long line of blocks should be 10 minutes averaged out. Assuming same CPU speed and you are the only one mining. But there is variance, sometimes it can take 1 minute to find the block and other times it can take 100 minutes. Even Bitcoin is like this sometimes. So 30 minutes is normal.