Bungie done goofed with the latest iteration of Iron Banner in Destiny 2 and the quest is quite buggy. Thankfully, there is an easy workaround unless it bailed on you completely.
Forging Iron is the quest that provides players with additional Iron Banner rewards in its first appearance in Season 17 of Destiny 2 . Unfortunately, it has managed to be bugged in more ways than one. Sometimes the quest will not progress on its penultimate step and sometimes it disappears completely.
If it disappears, there is currently no fix known to us but if it's simply not progressing on the fifth step, you can fix it with barely any effort. The fifth step, out of six total, requires players to participate in Iron Banner matches while wearing Iron Banner armour.
However, if you don't get any progress after a match, it is almost always the same issue - using Iron Banner ornaments. Normally, Guardians equip these to boost the points they gain from a match but they are preventing the progress of Forging Iron's fifth step for some reason.
Simply unequip any Iron Banner ornaments you currently have on you and the quest will progress normally as soon as you get into the next match.
Furthermore, you are free to use any other ornaments as they don't cause issues. In my own experience, I equipped ornaments on all armour pieces and the progression was fine.
If you still want to get the extra points, you can use any Iron Banner armour you have as you get the same multiplier. It does not conflict with Forging Iron and you can equip any ornament you want on them, just make sure it's not IB ornaments.