My bike wont move the pedals just spin

I would guess that there is an issue with the cog ratchet teeth, if you say it’s new, then it’s either bad assembly or manufacturing issue of the freewheel. Come back to the shop and ask them to replace the freewheel, or if you don’t have warranty and want to learn how it works look up how to disassemble single speed freewheel and check the problem yourself.

I’m guessing your freewheel pawls aren’t engaging. The solution is to replace your freewheel. A replacement should run $15, but you will need a freewheel tool (about $ 15-20) and a long handle wrench.

There is a chance that the current freewheel might not have the tooling (notches for a special tool) to remove it, so you’ll have to basically take it apart using a pin spanner and vice.

There is a park tool article about it if this is the case:

https://www.parktool.com/en-us/blog/repair-help/freewheel-destructive-removal