Possibly cold welded healing abutment: what to do?

I installed a BioHorizon tapered Laser Lok 5.8 x 12mm with an internal connection in #31 site [mandibular right second molar; 47] 2 months after tooth extraction and placed a direct healing abutment. The post-op was uneventful and it seemed to heal well. After 2 months, I removed the healing abutment and placed an impression coping for pickup impression and afterward replaced the healing abutment. When the patient was recalled for crown insertion, I could not remove the healing abutment. I tried using a torque ratchet and then a machine driver with 70 N anti-torque but the healing abutment would not budge. What can I do to remove the healing abutment?