Thanks for updating in. I apologize for the confusion. Lets go back to your issue. In your homepage, you have applied one page navigation for the menu. Please be aware that the correct way of setting the one page navigation is to have two separate menus. One menu will be used as your primary menu and the second menu will be used exclusively for the one page navigation option for your homepage.
In order for your portfolio items to have the default and working menu, you must assign the menu as your primary menu. And in your homepage, you will need to edit the homepage and find the "Page Settings". This section is the place where you can find the one page navigation option for you to assign the second menu, the one which will be used exclusively for one page navigation. If you are using Cornerstone, please edit your homepage in Cornerstone, go to the settings tab, Settings > X Settings and find the one page navigation option.
If you want to review how you can set up the one page navigation, you can check it here: https://theme.co/apex/forum/t/features-how-to-setup-one-page-navigation/96/1
Hope this helps.