first of all, welcome here in our forum and welcome at Navigraph.
I have checked, if there approaches are existing for EGTC or not and yes, all approaches are included and also selectable:
Here from the WorldMap:
and also the charts are available:
In other words, as you see we offer the data but it could be, that you do something wrong in the GTN750 or the GTN750 has a bug which doesn´t load the corresponding charts.The best in this case is, to ask in their forum/discord … as you see, the data are available, so it should be possible to load the charts in the GTN750 (when the developer had made all correct and you´re logged in correctly).
Sorry, can´t say more in this case because this is out of our scope. Let me know, when you have any other question and/or when you know the “answer”. It also good for us (and also for the community here), to learn how 3rd party issue can be solved