The Silver ingots from this mod can't be converted into Silver blocks and same goes for silver nuggets can't be made into silver ingot(of I&F's), if you could just add a crafting recipe with silver ingot from this mod and convert it into Ice and fire's silver ingot that might solve the whole issue.

Ice and fire's recipes are not support 'tags'.
They only accept exact items.

It need change from Ice and fire mod.

silver_ingot_to_silver_block.json

{
  "type": "minecraft:crafting_shaped",
  "category": "building",
  "key": {
    "#": {
      "item": "iceandfire:silver_ingot"
    }
  },
  "pattern": [
    "###",
    "###",
    "###"
  ],
  "result": {
    "item": "iceandfire:silver_block"
  },
  "show_notification": true
}