The most likely reasons for the denial of the renewal of a Green Card are:
1. Errors on the form I-90.
2. Involvement in illegal activity.
3. False or dishonest statements on the form I-90.
If the person has consulted an immigration lawyer, he should have some idea of why his application for renewal was denied. By now he should also have received a letter from the USCIS describing the reasons for the denial.
At this point, he should consult a (different, better) immigration lawyer.

