The reason for the import error is because Arena uses Wizards' official set codes. So the Clifftop Retreat's set code should be DAR instead of DOM because for some reason DAR is Wizard's official designation code for Dominaria. It would also trip on the other Dominaria cards in the list, but Clifftop Retreat just happened to be first on the list.
1 2019-05-07 18:41:58
Re: Export deck to Arena, imported Japanese Alt Art promos (9 replies, posted in Announcements)
2 2018-06-13 14:03:13
Re: Alpha testing: Details in decks (30 replies, posted in Announcements)
Is Commander Anthology 2 being added soon to the card set list?