Hey there! TCGPlayer accidentally broke the ability for MTG CB and other sites to mass post cards to their cart.
They think they'll have it fixed, at earliest, in late May. I've made a workaround, though!
Step 1: Copy the contents of the box below.
Step 2: Click here and paste the cards on their page!
As always, you'll need to use their Cart Optimizer to specify which set you want for each card.