Hi Alex,
Thanks a lot for reaching out and thank you for using BoldGrid Post and Page Builder for WordPress!
I’m sorry to hear you’re having trouble displaying your primary menu. Post and Page Builder doesn’t have any control over your menu settings that would be something handled by your GeneratePress Theme.
If you recently switched themes you may need to reconfigure your menu locations but it would be best to reach out to GeneratePress support for direction on how to do so.
I hope this helps!