Blizzard have announced they’re temporarily closing the newly linked Auction House due to a critical bug. You can read about all the changes that arrived with the new patch here, including the region-wide commodities AH, as well as it arriving on the companion app.

AH (Source)

We’ve got a critical bug with the Auction House in 9.2.7, and we’ve closed the AH while we investigate and decisively fix it.

We’ll track this issue closely and provide any further updates as soon as we have them.