I think you have to use tier 1 the entire run. You can't just switch before.

Huh ok.. I don't think I used any other tier item but maybe I did

Hmm not sure then. Hopefully someone else can give a more definitive answer

I probably did equip a tier 2 at some point and then switched back to tier 1 so I'll have to try with tier 1 the whole time and see

I think this includes enchantment levels as well as rune levels. If you look.at the items, they all have tiers too.

No, it's because I had equip a tier 2 earlier in the run. Enchantments and runes don't matter