From my knowledge IDEX doesn't charge for listing fee, they list tokens freely, they decided to choose quality over revenue although this isn't always the case because they have listed severally worthless toknlens on their exchange.
Here's an official statement from them,
The Aurora team carefully evaluates every token submitted for listing on IDEX within two weeks of submission. If a token meets our listing criteria, IDEX will request a meeting with the token’s team via webcam to finalize details. Pending this in-person meeting, the token will be added to IDEX and announced via our Twitter channel when it is available for trading.
If your token is not listed within two weeks of submission, it is safe to assume you did not meet our listing criteria at the time of review.
Source:
So that means there's nothing you can do but wait patiently for your project to be evaluated.