I'm getting error 4577.k.No.ar when trying to add a mobile variant

To fix this error message:

1) Right-click on  your Navigation Bar > Edit Navigation Bar

2) Uncheck the option "Site Navigation Bar"

3) Click ok, try creating the variant again.

If you are still getting this message afterwards, save your project file (File > Save as) and send it to support - https://www.xara.com/contact-us/