Can't improvise commanders

[NapoleonBorn2Party]

Couldn't cast Urza, Lord High Artificer from command zone after activating Archway of Innovation, even though i had enough artifacts + islands to pay for it's costs

[PurpleCrowbar]

[[Urza, Lord High Artificer]] [[Archway of Innovation]]

[github-actions[bot]]

Urza, Lord High Artificer - (Gatherer) (Scryfall) (EDHREC)

{2}{U}{U} Legendary Creature — Human Artificer 1/4 When Urza, Lord High Artificer enters, create a 0/0 colorless Construct artifact creature token with "This creature gets +1/+1 for each artifact you control." Tap an untapped artifact you control: Add {U}. {5}: Shuffle your library, then exile the top card. Until end of turn, you may play that card without paying its mana cost.

Archway of Innovation - (Gatherer) (Scryfall) (EDHREC)

Land Archway of Innovation enters tapped unless you control an Island. {T}: Add {U}. {U}, {T}: The next spell you cast this turn has improvise. (Your artifacts can help cast that spell. Each artifact you tap after you're done activating mana abilities pays for {1}.)

[Ikatono]

Just ran into this. I was able to use Improvise to pay for my commander, but I couldn't start casting unless I was able to pay for it without Improvise.

This was also with Archway of Innovation.