Not Getting any new missions for lunar reveal

There was a limit on free mission it was 10 for a garanteed 100 token.

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I'm trying to grind these envelopes but i dont have any missions to complete

It seems like you have finished your available quests.

To confirm if it's a bug, of if you've just run out of quests you can find the full list of available quests under their 2019 Lunar Revel post here: https://na.leagueoflegends.com/en/news/game-updates/special-event/learn-more-lunar-revel-2019