Hi Nidua,
Just like baking, other ingredient are sometimes needed to make a flavor pop. Make sure you use a sweetener with the coffee. Coffe tends to have a little bitter taste sweeter activated more tastebuds. I'm not familiar with tfa's coffee. I just made " coffee espresso" from flavour art. It smells like a skunk in concentrate form, really. I made a batch at .5% FA coffee espresso 3% Bavarian cream and .5% EM to further sweeten. Omg it's awesome lol. I'm going to increase the espresso flavor to 1% on the next batch.
Try your batch at 1%. Just let it sit a day it won't need to steep a week.
Regarding your flavor, what are you using for an atomizer. If you're using a vivi nova try just a plain boge cartomizer. I'm jaded I hate vivi novas. Atomizers play a huge roll in getting the right flavor.