Extrusion problem?

[NOTProps]

Hi!
I'm a newbie here on this forum. I have a I3 PRO B and since 2 days, my printer has started to not extruding correctly. I don't know why but on the center of the heat bed it doesn't place material. As you can see in the attached photo.

For the print I used these parameters:
Slicer: Cura
Level height: 0.15
First level: 0.3
Speed: 20 mm/s
Extrusor temp.: 210°
Bed temp: 65°
Infill 15%
2 perimeters
grid infill: 15%