My sensor light came on my air pressure is right and it still won't go off, what do I do?

tire pressure sensor came on while vehicle was in motion on the highway at 55+ miles and above. it seems to only come on during those speeds. my husband checked the tires they have enough air as recommended (see side panel on your doors for recommened amounts) had to take it again and they had to remove all tires and checked for something else. after that they somehow managed to fix the problem