Can't print properly anymore

The 3D printer is almost new and I could print properly at first but after trying to calibrate many time there is definitely something strange.
Here is picture of my last print. There is no material printed on the center of the bottle even if the 3D data have no problem at all.
When I try to do the Fine Tune Z-Offset wizard (second picture) the bed seems to be sloping a little bit.
But I tried many time to adjust that by calibrate with the screw under the bed and I can't make it perfectly flat.
And I guess it doesn't have to be so perfectly accurate to print fine right?
By looking my pictures and with my description, if somebody have an idea that could help me it would be greatly appreciate.

 

Any luck with your printer? I have a 25 day old machine and have had 2 successful prints out of a few dozen attemps.