Remember to open Fireteam Builder preferences for Crossplay! (Destiny)
I've got a Valut of Glass event going for Sunday, but realized that although I set it to IRL (pending a tweak to the system, I thought it would be the most inclusive), I personally had IRL notifications turned off. Realizing that many folks might be in the same boat, I switched it to Xbox, just in case...
Be sure to check your preferences now that Crossplay makes it mostly irrelevant!