Solved PLA Warping Tips Needed

Novice in need of direction.
Robo3D R1
Matter control 1.5

Printing a flat/thin 6" square box lid. Every attempt has the corners warping up preventing the lid from fitting properly.

Tried blue masking tape on the bed
Tried hair spray on the bed
Tried elmer's glue stick on the bed
Tried nothing on the bed

I'm thinking I need to adjust some settings. Currently...
Extruder Temp = 217 degrees
Bed Temperature = 50 degrees
My MEDIUM QUALITY PLA setting has a Z OFFSET of 0.83mm

Could any of these settings be adjusted to reduce/eliminate PLA warping?
Anything else I should be checking/adjusting? (see attached)

Thanks... this forum is awesome.

 

try no heat to the bed.
Hairspray
190C nozzle temp.