7 Week Old Chicks: Refuse To Walk On Smooth Surfaces?

[Bumblebee-chicks]

We have three, 7-week old serama chicks. Two are pullets and one cockerel. They are very sweet and cuddly but the two pullets refuse to walk on our tile or hard wood floors. They walk in the coop with fluff, our laps, couches, and rugs no problem. They sit down, cry, and scoot backwards. They are our second set of chicks we have raised and our first chicks (two were the same breed) had no issues. We are trying to desensitize them and are going to introduce treats to try to train them it's okay. Any help appreciated. What should we do to fix?

 

[nuthatched]

They can't grip.
At 7 weeks, they can go outside, where that won't be an issue.