it worked fine before but on my way to work and home it never got warm. Is this a common problem? Any ideas on what might be wrong?

 

thermostat stuck open or a clogged heater core.

 

Non-working thermostat is possible.
An alternative repair possibility is to flush the core.

Carefully(!) remove both heater hoses near the water pump.
Gently bend the top one back and down to point toward the ground at the open area just near the starter.
Use very low pressure air, a bicycle pump with nozzle works in a pinch, or you could just blow with your mouth.
You want to reverse-flow flush the heater core.
If air does not go through, your core is plugged. If it goes through a little, fill the hose up with water and flush it over and over 'til flow is restored.

To much pressure will bust out the core, so go easy!!

Some use a bit of Vinegar to help flush out residue from hard water deposits.

Take the time to wash out your reservoir tank too. It can get nasty in there if you haven't maintained things.

Make sure you fill up the system, and fill the (now clean) reservoir tank completely after you button it all back up.

 

Thanks, I will try in the morning