Solved.
One day all working fine, next day getting error.
Followed advice from this thread: Connection problem can't set com-state - #2 by ptillisch
Still not working after CH340 driver re-install.
Noticed a comment that it is usually bootloader problem. I was using Old Bootloader (which is correct), but I tried de-selecting it, tried upload (fail obviously), then selected Old bootloader again and it worked !
Frustrating and weird, Having the correct settings isn't always enough! Sometimes you have to flick random switches and then try the correct setting again!
Hope that helps someone 