We are installing a roll-in shower. We poured the floor and after 2 days it has several cracks in it. I am not sure if they are all the way through.
Is there any way to fix this or do we have to take the cement out and start over?
Unfortunately, your real problem here actually isn't that you have cracks in the cement; it's that your cement has developed several cracks in 2 days. They are a symptom indicating that the cement is weak (typically because it was not mixed correctly; most often, it's too wet). Nothing you do to repair the cracks will fix that weakness.
The right thing to do in this case would be to take the cement out and start over.