I was making some encounters and was using some monsters from that book, but for some reason I cannot view the stat blocks even though I own the book. Hitting the "view in marketplace" button even pulls up the full stat block. I wish this bug would be fixed.

Double check that your Account Entitlements are in sync: (https://www.dndbeyond.com/account/marketplace).

Just checked and for some reason it still doesn't let me view the stat blocks. Only with MooT though.

Weird. I know there was a similar issue with either  Mordenkeinen’s Tome or Volo’s Guide too (don’t remember which one). I don’t know if that got resolved yet or not, or if this is related at all though.

I also have this issue. Entitlements are in sync.

I am also having this issue but with Eberron: Rising. My entitlements data is in sync

Gone through a few of these threads so I've done the trouble shooting already and can confirm I'm also unable to look at stat blocks from MOoT, MToF, ERftLW, EGtW, IMR, LR, PotA, as well as the bizarre issue of being able to use some stat blocks from PotA but not others and the bizzare issue of being able to use all stat blocks from FToD except for the Adult Sapphire Dragon. I don't expect a quick fix with a bug this scattered. Just a wild issue, I can pull up new windows with all of their stat blocks but the ease of having them in the encounter builder will be missed

Mordenkainen’s Tome of Foes also does not show for me.

An update my licenses seem to all be working again for the encounter builder. So that's nice.