They were bought early on then support stopped due to the arms embargo.
Here's info from SinoDefense.
S-70C Black Hawk Multirole Helicopter
The PLA Army Aviation Corps operates around 20 Sikorsky S-70C multirole helicopters, which are known as the UH-60 Black Hawk in the U.S. Army. The PLA purchased these helicopters in the mid-1980s. Despite the speculations that the PLA faced some difficulties in obtaining the necessary spares to keep these helicopters operational as a result of the U.S. sanction after 1989, some, if not all, of these helicopters remain in active service with PLA today for tactical transport roles.
The purchase of the 24 Sikorsky S-70C Black Hawk multirole army helicopters is one of the most notable military cooperation programmes between China and the U.S. in the 1980s honeymoon of their relations. To help China modernise its ground forces against the Soviet Army, the U.S. offered its army helicopter to the PLA. Two major U.S. helicopter manufacturers, Bell and Sikorsky, were chosen as main bidders for an immediate deal of 20~30 helicopters, and a possible purchase of over 100 additional units afterwards.
Sikorsky sent one of its newest S-70C Black Hawk (known as UH-60 in the U.S. Army) multirole helicopter as a counter to the Bell 204 (known as UH-1 in the U.S. Army). Both helicopters flew in most regions of China, including Tibet which is infamous for its harsh weather conditions. Eventually the PLA chose S-70C and a deal of 24 helicopters were delivered to the PLA Air Force in 1985. In 1987 these helicopters were handed over to the newly founded Army Aviation Corps.
Both Sikorsky and the PLA expected deals of additional helicopters after the successful deployment of the initial batch of the S-70C in China. However, after the 1989 incident, the U.S. government froze all military relations with China. The remaining helicopters in the PLA were also hardly well maintained due to the difficulty in obtaining necessary spare parts from the United States. Unconfirmed reports indicated in 1992 that these helicopters were offered for sale, but it appeared that the PLA managed to keep them flying. In 1997 and 2002, Sikorsky tried to persuade the U.S. government to waive the sanctions, but was rejected by the White House.
Today the S-70Cs are still used by the PLA, and were spotted in many occasions during the military exercises in the 1990s. They appear often in the PLA’s publicity photos and video images of Army exercises, and have been reported to be flying in high-altitude locations in Tibet. At least 3 helicopters have been lost due to bad weather and pilot faults. As these helicopters begin to reach their flying life hours in the coming years, they are likely going to replaced by the Russian Mi-17V5 in the future.
The S-70Cs in service with the PLA are generally identical to the UH-60s in the U.S. Army, apart from their specially-designed gear box which were derived from the SH-60 Sea Hawk.
The S-70C is equipped with two General Electric T700-701A turboshaft engines. The internal fuel tanks have a capacity of 1,360 litres. Auxiliary fuel can be carried with 1,400 litres in two internal fuel tanks and 1,740 litres externally.
The S-70 is equipped with a voice and data communications suite including VHF, UHF communications. The S-70Cs sold to China were specially enhanced with the LTN3100VLF weather radar accommodated in the under-nose radome.
The cabin provides accommodation for eleven fully equipped troops or four litters (stretcher patients) with a medical officer for medical evacuation missions. The cabin is equipped with a ventilation and heating system. The S-70 can carry external loads up to 4,072kg on the cargo hook -- for example, a 155mm howitzer. The main cabin can be cleared of troop seats for transportation of cargo.
Flight Crew: Two
Length (Without rotors): 19.76m
Height (Without rotors): 5.18m
Blades: Main rotor 4; tail rotor 4
Empty weight: 6,191kg
Maximum take-off weight: 9,926kg
Maximum speed: 173mph
Service ceiling: N/A
Hover ceiling (out of ground effect): N/A
Hover ceiling (in ground effect): N/A