Recipes and Tags are only filled when you connect to a server / join a world, so by having your recipe invocation here you can't use the tags, you just end up with things like:

With the iron and gold tags being empty.
https://github.com/owmii/Powah/blob/1.15/src/main/java/owmii/powah/Powah.java#L45

Thanks!! i will fix it in the next release.