First Design can't be printed

Hi there!

I just made my first design in Affinity Designer, but the design was rejected.
Apparently, it can’t be printed.
But why? I don’t think it’s too complex or anything.
I made sure the lines where thick enough and uploaded it as a svg-file.

Can you tell me what’s wrong?

Hi! With SVG files, we check the flex print requirements. We can only accept a design that has 3 paths or fewer.