It seems that you have used third party menu plugins rather than our default menu. We cannot make sure all the third party plugins are compatible to our theme.
I am having this problem. I am not using a third-party menu plugin. I have configured submenus. They show up. However, there is a gap between the main menu & the sub-menu. I cannot click on the submenus. I see other posts regarding this issue. However, I don’t see a resolution. I cannot use this template the way it is. We need functioning submenus.
I have recently upgraded to WordPress 5.4. However i’m not sure that the problem started there. When I access my website via mobile/tablet, I can select menu and then choose by Sub-Categories under Portfolio.
However when I access via a PC then the dropdown selection appears when the mouse hovers over Portfolio but disappears when you move the mouse to the desired selection thereafter. https://gpsphotography.co.za/