Solo mining on created altcoin: not able to create block
You should run instance of node in atlest two diffrent machine and both of the need to get connected via blockchain.The reason behind need of atlest two diffrent machine is consensus protocol. 
To add another node,


  Run same instance of code on second machine add following line in conf
  file: 


addnode=*ipOfSecondMachine*



  To check if node is conneceted


getpeerinfo 


is what you need 

Then go with normal  steps of minning, 

ps: if you are trying to mine srypt based coins like ltc then i recommend sgminer