Just noticed during some play testing that when you first start and drop down your Seed Lander, robots can't be placed until the Command Center is built and operational. This is a little silly and unintended -- it'll be corrected in the next update.
In the mean time, you can just progress your turns until the CC is built and drop your Cargo/Colonist landers. This stunts early development a bit but is a work around if you don't already have an established game.