Thanks so much for reaching out and thank you for using BoldGrid Post and Page Builder for WordPress!
Post and Page Builder wouldn’t have any effect on the menu structure at all that what leads me to think this issue is directly related to your theme change. I think the issue is stems directly from your theme change.
I see you’re using the WooCommerce StoreFront theme which likely has a different “Menu” configuration. You could try switching back to your old theme or setup new menus in Storefront from the “Menus” section of your WordPress dashboard.
I found a video on Youtube on setting up the Storefront theme that you might find useful.
I hope this helps. Please let us know if you have any other questions for us.