Figured it out. Falling_Sand was changed to Falling_Block, so the command would be:
/summon armor_stand ~ ~1 ~ {Passengers:[{id:"Falling_block",Time:1,Block:"minecraft:planks",Data:2}]}
Figured it out. Falling_Sand was changed to Falling_Block, so the command would be:
/summon armor_stand ~ ~1 ~ {Passengers:[{id:"Falling_block",Time:1,Block:"minecraft:planks",Data:2}]}