The error "Some shapes are out of print boundaries" is shown when a part of the PNG file is out of the dotted print area. This could be the clear space around your design or the design itself.
Our systems cant differentiate between the two so this error or warning is shown so that you as a user can check that the part of the PNG file that you want printing is within the print area.
Once you have looked at the print file and checked that the design will print correctly you can accept this warning and proceed with the design.