I'm using the most recent version of Magiculture 2 (2.2.4), and though both my client and server configs have the inventory button enabled, it doesn't show up. I was hoping to allow my players to bypass the magic level requirement that the modpack requires.

I'm not having this issue, please check if your server has two waystones.cfg files (one lower-case, one upper-case), there seems to have been a problem at some time in the past: #107

It could be that the config is being loaded from a different file than expected. The upper-case version should be the one the server uses, and lower-case should be deleted.

If that's not the case it might be conflicting with another mod, what other mods in this pack do changes to the inventory screen?

You're absolutely right, I do have two copies of waystones.cfg, one uppercase and one lowercase. I'll delete the extraneous one!