To start you'll need a new hammer (almost) every time you get to a new metal - Customer buy what your hammer level is or cheaper - Alloys are an exception, which unlock all metals (seemingly)
Additionally. if You're trying to hit heated ingots on the anvil and its not connecting or it is but its not making the right item associated with the right number of ingots, Then something may be in the way of the anvil, or, the anvil may have accidentally swallowed a heated ingot at some point or encountered a hiccup where it assumes it has.
I don't readily know ways to fix this - But you can try taking a pole grip and swishing it around inside the anvil, then removing it from the area, or using your crates near the anvil and seeing if you get a reaction that allows you to close it, and then trying to pull it away.
If you know you have a bunch of objects near the anvil, Simply first try clearing the space of these objects, An item may not even appear close enough to the anvil to count, but in reality, its hitbox/connection triggers are actually in the way and you just can't see it (possibly)
Then the next time you put up ingots open the radial and ensure the correct Group is /possible/ even if it is selected.
You'll see "Large Blades" for example if you have 3 heated ingot on the anvil and go to select blades.
If you see "Large blades" and only have 2 ingots on there - The anvil must assume there's another despite there not being. (Again, Aside from fishing around into a solid object, I don't really know what to do here)
If you have 3 on there and only see "normal" or "Small" - then something is blocking the Anvil from reacting properly to the other ingots. - Example - If an item is sitting ontop of one of the ingots - The anvil will not react properly. This is a readily apparent example - But It's possible a grip could be near by and causing an issue too, even not being near the top of the anvil.