The appointment calendar is inactive

We have been using this appointment calendar for several years and didn't change anything, it worked without problem. Now not only the hours are inactive, but the days too. If You try to choose another day, the buttons are inactive (it opens only one time). By the way, if You try to make an appointment on smart phone, everything work, but on computer it is impossible. This is not our computer problem, our client complained about that. The problem appeared aftter automatic wordpress update. Can You help??