Have you been smoking marijuana? If so, take a break from marijuana for a couple of weeks and reduce your usage of it when you are planning a DMT trip. Sometimes marijuana can inhibit the DMT experience quite a bit. Drinking often can have the same effect. I find smoking marijuana after a DMT trip enjoyable.
Sometimes DMT just blocks you out. It is best not to have expectations about your experiences, although I know how disappointing it can be to end up in some waiting room. Take a break from DMT for a while. Maybe try a LSDMT combo?
Intent is another thing to consider. Maybe you didn't have much on your mind at the time. Focus on what you would like to achieve with any given trip. Sometimes just this kind of focus can enhanced the overall experience. Think about what kind of trip you want to have and try and create that within your mind before your journey. One word is all it can take. If you want to have fun think "Fun! Fun! Fun!" over and over just before. You may be surprised how affective this can be. At least for me it works well.
Good luck... not sure if this helps or not. Different things work for different people. I have been in the waiting room. It can be boring. You have to become the life of the party when this happens. Laugh in the waiting room.
Ha! Ha! I am in a waiting room in hyperspace! WTF!
Here is some nice music to enjoy next time you are there. ->