screen sharing stopped

Screen sharing was working fine until today. I can no longer us MBP to see screen on Mac Mini. Remoter VNC on iPad also cannot connect to Mac Mini. Remoter VNC can connect to MBP.

System prefs on Mac Mini look ok, ie. screen sharing on, and firewall settings allows screen sharing. Worked fine until today. Have trashed screen sharing prefs.

Ideas please.

PS I can log on from MBP to Mini and mount Mini directories on MBP, no screen sharing. So they can connect in some ways.