There is a perfect height that the nozzle must be at in order for the PLA to stick to the bed this is where the nozzle should be.
I found that if you print with a material that is less forgiving about layer height it is best.

You may note that a lot of 3D Printer users print on blue tape while I chose to print on Vinyl Transfer Paper Tape, Why you may ask.
Because I have a Vinyl Cutter and have lots of Vinyl Transfer Tape mostly it covers the entire bed in one pass...

You are not the first or will you be the last to have this very simply though sometimes hard to learn adjustment.
Shown below is an image of using Tape in lieu of another type of printing surface.

T1.jpg

It took me a long time to get the nozzle height correct and found two changes that helped me the most.
1. Printing on Blue tape or in my case Vinyl Transfer Paper Tape.
2. I 3D Printed a z-axis spring loaded proximity sensor holder.
3. Enabling the function baby stepping also allows me to quickly see if the layer height is correct and do fine tuning while 3D Printing a 2 line Skirt.

Compare.jpg

I also changed my Proximity sensor for a lower profile sensor shown in the image above.
The sensor has a thumb screw nut for easy adjustment of the proximity sensor height.