I have more than the 20 medals it says requires, Had them for more then one reset but each next day I can not go to tier 2. ADDED: this is the dungeon event, the daily siege did update to tier 2.
The event dungeon need to complete its 3 day cycle to register the upgrade. It will upgrade to Tier 2 with the event dungeon refresh tomorrow.
Thank you, they need to update the tooltip to that because it says next day