I have the buttons (shop, deck builder, reward book) but I can't use them most of the time. I was lucky a few times and got into the reward book, where I unlocked the first sets of seasonal quests and got -once- into the deck builder to make a new seasonal deck. Can't get back in there to make adjustments, though...so it's not really fun playing. Also not being able to go to the shop after a new expansion came out is kinda.........
EDIT: imagine reading https://twitter.com/i/web/status/1277926106126004224 after you just complained about those features not working.
Still, being able to access the deck builder would definitely be nice, especially since some people are already playing with some of the new cards.
This is such a bad feeling. I can't even open my pre-ordered Master Mirror kegs. I spent like 60 bucks and am not even able to open the kegs more than four hours into expansion. Great job. They always have all sorts of bugs when the expansion starts but not being able to open kegs you possess is well over the top.