Who do I contact in order to find my 2018 tax return money I have never received?

You asked:  "Who do I contact in order to find my 2018 tax return money I have never received?"

It depends. More information is needed.

A Federal refund, state refund, or both? 

Did you file the 2018 return last year, or did you only file it more recently?

Is this your first time checking on it, or is there more to the story?

First you need to see if it was successfully filed.   Was the 2018 return prepared in Online TurboTax?

If so, log in and at the Tax Home scroll down to the section "Your Tax Returns & Documents."  Expand that section and choose tax year 2018.   What is displayed for the status of the 2018 Federal return--which of these terms:  accepted, rejected, printed, started, ready to mail, or what?

And what status does it show for a state return (if applicable)?