I made the worst mistake to install TightVNC to use remote desktop from my laptop that is by default installed. I didn't know that VNC is much better but when I installed it on some tablets I saw that it doesn't create another desktop but accesses directly the existing one, so I can see exactly what happens on a monitor or TV directly connected to Raspberry. This is great. I installed on laptops VNC and I can connect to one of my raspberry. On the other Raspberry I installed TightVNC.
When I try to enable the VNC into the configuration menu, it looks like it is already enabled but the radio-buttons can not be used. I can not change, this option itself is disabled and grayish.
I know this problem was debated earlier but may be somebody knows a quick fix now without reinstalling the OS. I have a lot of work and libraries installed now and I do not have time to reinstall everything in this moment. Can be the TightVNC the culprit? I installed it to use remote desktop. But the Raspberries already come with VNC by default to use with VNC viewers from all possible tablets, phones or laptops.