ACTUAL SOLUTION (from MiniHorseRodeo):
Solution for Everyday Explorer in Microsoft Bingo (Windows 8)
"Easiest way to get this is to always play on the highest venue you have unlocked and only using your keys on said venue. The higher the venue, the more coins, tickets, and keys you can win, thus allowing you to build up your stock and stay in the game until you have blacked out all boards. In doing so you will end up with 50+ chest at the end. you also gain the most xp per game by playing on the highest unlocked venue, using bingo and 2x power ups greatly increase your per game xp and rewards."
This achievement is now obtainable and should unlock retroactively once you install the newly released update (version 2.2.12142.0).
Dec 16, 2015:
"Whooooaaaaaa! Hey, everyone! I know it's been a hard couple of months, but I've got word that there's an update released today that should fix everyone's achievement issues (as well as some other issues with performance, network, and purchases). The even better news is that it should be retroactive, and you should NOT have to earn your achievements again!
Please make sure you update. You may not see the update available until tomorrow, though, but keep checking the Store for the update and let us know how it goes. :) Thanks again to everyone's patience! For now, I'm going to verify this post so that everyone can see that an update has been pushed without digging for this post on page 5. If there are any other issues noted, I'll remove it so that no one thinks this is resolved. :3"