I have written a simple guide for getting started with mining, all the things you need to make sure you set in order to have a PC successfully mining, you canceck it out and compare if you have done everything required: https://steemit.com/steemit/@cryptos/getting-started-mining-steem-on-windows
If you follow it you should be all set for mining, the rest could be just bad luck... have you seen if you managed to mine a block on steemd.com ?