What should I do if ADP does not report my W2 to the IRS and they are reviewing errors?

it would probably do no good contacting ADP directly. you need to contact your employer. however, if your employer or ADP did not file your W-2 with the Social Security Administration, then the IRS does not know it exists and therefore it's not the reason for the review. More likely the IRS got a copy, but you didn't and that's the reason.

Did you get an official W-2 from your employer?  You would send the IRS one of the original copies from the W-2.  It's hard to get a W-2 and not have the information sent to the IRS.

Or, did you not get a W-2 because your employer did not send the info to ADP so ADP never sent the W-2?  That is also a bit odd, because if ADP was doing all the payroll processing, they would have the information.  Did your employer pay you informally, and was only using ADP for the W-2s?

Are there other employees in the same situation?  What about your state income taxes?

ADP can't submit to the IRS if the employer doesn't authorize it.  Something here doesn't make sense.  I would work both ends -- call ADP and ask what is going on, and call your employer as well.  You may eventually have to submit to the IRS, all your pay stubs showing your wages and withholding, and your bank records showing your deposits.  You can also contact the government department in your state that regulates employers (state labor board, Secretary of State or something else depending on the state).  The state can lean on the employer or punish them for non-compliance.