The wildfire Core Recipe requires Embers Copper Plates and they are not craftable.
We are running the latest version of ATM3. 3 V 5.3

Maybe you can use one of the ore dictionary conversion devices to convert a variant of copper plate to the Embers version?

The issue is that the recipe does not exist. I tried to use the industrial foregoing one and it did not.

I think this may be an issue of the "random chance" variation in Ember's Alchemy recipes that take some trial-and-error to get just right.

I think this because players have been able to craft the orb and ATM star even without reporting this as a blocker.

Even still, a new update 5.7 will be coming out soon, if you feel this is still a legitimate issue comment or make a new issue and we'll investigate farther.

You are still not able to do that. Altough there IS a method of creating those plates (ATM-3 ver. 5.11.2):

1. Obtain Uncrafting Table from TwilightForest
2. Craft something with available Copper Plates (from ThermalExpansion)
3. Uncraft that item in Uncrafting Table, but use small arrows in the bottom left corner to select a recipe with Embers Copper Plates
4. Use Ore Dictionary Exchanger from IndustrialForegoing to exchange ThermalExpansion Copper Plates into Embers Copper Plates, provided you placed a previously made Embers Copper Plate into "Examples" slot of the machine

You keep pinging someone named EMBERS, not sure they will be very appreciative, so just be careful with what you type after @. As for the wildfire core, I'll do some looking into it. We did not change how to get it at all, it is mod defaults for that. Also, it would be well worth opening a new issue on this instead of an old issue, since this was closed almost a year ago, and multiple modpack versions old. Last comment on it, the uncrafting table should have the uncrafting aspect disabled for dupe reasons. Looks like it isn't so that will be something fixed as well.

@nowifi4u One last thing, what modpack version are you using? That is always important to know. Don't just say latest though, that doesn't mean much to me, as I've seen issues in that past where what looks like the latest is not, causing confusion.