A bunch of my procedures do not work anymore at my airports. I've checked 3 airports that had this bug, Jeju (RKPC), Taoyuan (RCTP), Darwin (YPDN) and possibly others, there were just some of the few that screwed up my flight planning. They all are payware airports, but I don't think anyone else reported this problem at these airports and in the past I did not have issues at these airports either. All are marked as 2024 compatible.

What could be causing this? I've validated scenery library multiple times as well to no avail, unless there's a specific way I need to validate it by. Or need to clear cache or something?

I see no issues here using plain MSFS 2024 data. Navaids and procedures from add-on airports should be imported fine from MSFS 2024 (unlike 2020).

Do you have a Navigraph update installed in MSFS? If yes: also installed in LNM?
Is "Select automatically" selected in the LNM menu "Scenery Library" -> "Navigraph".
Scenery library fully reloaded and are the related VOR, NDB and waypoints available?

Alex