You, in your human form are vibrating at a very low density. You cannot tune into certain Dimensions because your frequencies are at a wide variance. As you become a more conscious and loving Being, you may begin to tune into other channels as your frequency increases.
At first there may be static, then you can begin to hear unintelligible chatter until finally you have clear reception. When you merge once again with your Higher Self, you will be vibrating at a higher frequency. At that time, you will be able to tune into several of the Dimensions that are currently beyond your range.