I have four fans - they all worked okay until yday - suddenly they all have stopped functioning - the red LED does light up when a button is pressed.

Have you checked the breaker panel yet? Do you have kids?

If all 4 stopped at the same time, it isn't your remote. You have a wire, that for some reasons seems to service all the fans, that is broken or disconnected. Check for a tripped breaker too.

Today in the morning after two days of malfunctioning, all four fans/lights have started to work again.I do not know how. I will let you know if the problem starts again. But, yes, to answer your question, yes I do have kids. And the day it stopped working, I had their friends at home too. So could it be something they had done accidentally?

I asked about kids because kids like to explore and fiddle with things. If they opened the back of your remote and moved even one of the many dip switches it would stop your fans from working. Let us know how things go for the next few days