I have a 2018 Fusion Hybrid and the fuel door will not open with the button on the drivers door. When I pull the cord located in the trunk the entire cabin smells like gas. Please help thank you

 

As you know, gasoline vapors are not good for anyone to inhale. Don't know the concentration level, but you should have that corrected ASAP.
The fact that the door will not release is a pretty good indication the two conditions are related.
Since this could be seen as an emissions problem , it may just be covered by warranty.

 

Our warranty just came up and is now expired. I work at a dealership but none of the techs have an answer. I feel like it has something to do with the fuel tank not depressurizing. But I could be wrong

 

You may have a bigger problem than you think.
I would try a different dealership !!!!!