PenciDesign replied
Hi,
This issue caused by you're using category mega menu for your AMP - it make the menu can't be validate on AMP.
We've said about this issue in the documentation for Soledad theme here
please go to Appearance > Menus > create a new menu for your AMP ( which don't use category mega menu ) > scroll down and check to "AMP Menu".
Best Regards,
PenciDesign