I claimed the triumph in-game but can't claim Galactic Magpie for some reason. In case it helps, I did Vow several days ago, so I'd assume Bungie servers have had plenty of time to sync with Bungie Rewards.
In case it's necessary, here's a screenshot of me having already claimed the triumph.
https://cdn.discordapp.com/attachments/720055384131239967/1007798124049354772/dlm2.jpg
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Hello there Try logging out and back in. I can see it u locked in your collections