I was accused of stealing from my former employer. We made payment arrangements. If I cant make payments now is it civil or criminal?

The short answer is both.  Your employer does not decide whether to pursue the criminal case, the local prosecutor does, although your employer can certainly urge the prosecutor one way or the other, and the prosecutor would probably not pursue it if your employer didn't want to.  Whether or not you make the payments, the prosecutor can pursue a criminal claim, but it is likely that he/she would not (and probably would never know about the crime) if you made the payments.  If you don't make the payments, it is far more likely that your employer will go to the prosecutor and seek to have you prosecuted, and far more likely that you would be.  Your employer can also sue you civilly  for damages.