Piaggio P-180 pilot reported aircraft loss of nose wheel steering during taxi in. Aircraft was towed to parking.

Narrative

On Day 0; at approximately XA:50; I was Pilot in Command of Aircraft X and landed at ZZZ. The approach was normal and the landing and rollout was also normal. I landed on Runway XX and exited the runway at A6 to the right. After crossing the hold short line; my co-pilot read the after landing checklist and it was completed. We were cleared to taxi to FBO and I proceeded to turn the aircraft to the right and proceeded on taxiway A. After taxiing approximately 75 to 100 feet; the aircraft started turning to the left. At that time; I thought we had lost the steering; which has happened numerous times in this aircraft. I made a comment out loud that we had lost the steering and proceeded to push the off button and immediately pushed the button to turn the steering back on; which is what I have done in the past. There was no response on the steering and the aircraft continued going to the left. I then starting pressing on the brakes; attempting to stop the aircraft roll and also applied full reverse throttles. This did slow the aircraft down; but was unable to completely stop the roll. The aircraft proceeded to turn left and the left main dropped off the taxi way into the sand. When this happened; it caused the aircraft to turn harder left and the nose wheel then exited off the taxiway and then came to a stop. My co-pilot then notified the Tower that we had lost steering and brakes and the aircraft was stuck in the sand. I then did a shutdown of the aircraft and airport ops arrived. The airport ops made contact with a towing company and they arrived at the location and was able to get the aircraft out of the sand. The aircraft was then towed to parking and was chalked. I was not able to see any damage to the aircraft or to the landing gear.