I have cm3 on my 1.12.2 server, and I can't get the field projectors to recognize the block of iron+redstone.

Probably a duplicate of #271.
If it isn't, you'll need to be more specific. "It doesn't work" does not help anyone.

No, I had made that initial mistake as well, I increased the size to be proper, but when I try to throw in the catalyst, it does nothing. I click the projector and it states, 'no valid recipe'

I tried this in creative in single player and it worked just fine. Trying to get access to the server to give you more info.

Does the server maybe have different recipes configured than the client?

No, it's literally an exported default setup of mods from multimc, cm3 was added manually and the server was restarted to load it. I was hoping the recipe unpack and a /reload would fix this, but alas, I wouldn't be that lucky :)

Please check anyway, because it sounds very much like this would be the issue.

What I'm trying to work, on, I contacted my buddy since he's the only one with access, currently in class I imagine, I will let you know ASAP.

ok, I did the unpack recipe command prior to the server being rebooted, but a restart fixed the problem, perhaps the mod isn't initializing the recipes on first use, server wise?

You should only do the unpack recipe command if you intend to modify the default recipes, i.e. if you create your own modpack - the recipes on the client and on the server must be the same or you run into this issue.