We have a 2003 Craftsman riding mower. The mower will start but you cannot engage the gears. Any help?

You need to make sure that the belt that controls the blades is there and working. That would be the first thing that would usually go wrong.

If it is there and looks like it is in place try pulling up on the pedal while it is running and in gear and see if it engages then. If it does then maybe you can adjust the belt tensioner to get it to work. Otherwise you may have a stretched belt that needs replacing.

If pulling up on the pedal doesn't make it move then you will need someone to help you. While you are trying to make it move have someone watch underneath and see exactly what is happening. Is the belt moving, is the pulley on top of the rearend moving etc...

See what is happening and let us know. We can go from there.

I could not engage my blades. I replaced the deck drive brake arm. It was bent and not allowing the idler pulley to engage.
It could also be the clutch cable. I had to replace that after I broke it trying to force the blades into gear. If so try EBay. Don't pay manufacturers price.