This could be caused for a number of reasons.

In the first instance, make sure that you've set up the TSM Desktop Application and TSM addons correctly. This includes selecting the correct WoW directory in the app, picking the correct realm on the TSM website and installing all of the official TSM Addons then ensuring they're enabled.

Here is a handy step-by-step guide on getting everything set up from scratch: Setup TSM Desktop Application

If you're still not seeing any pricing information in your tooltips after carefully verifying each of the steps in the guide linked above, doing a /reload in-game and you're sure you're logged in to the correct realm, stop by the TSM Discord Server