If you are going to cruise learn how to check the power step by step. Use a multimeter and first check there is power coming from the shore power post, then connect your shore power cord and check if there is power at the boat end of the cord. Then connect to the boat and check if there is any power coming into the AC circuit panel on the boat. If you do not have a power light on the panel you may have to open the panel up and check from behind. If you have power coming into the on board panel there must be a switch or breaker you need to turn on.
If this is beyond your skill level hire an electrician and watch carefully. If you cruise you will be doing this from time to time as the power is out from time to time at the shore power posts.