Please consider that the addons of UberMenu are outside of our support scope. We do support the UberMenu itself but not the additional features that you add to the plugin. Having said that, I checked the case by changing the Theme from Pro to 2017 and tested the menu, and the Sticky Menu is still not working. This shows that there is no conflict with the UberMenu Sticky Addon and our theme, and there is a problem with your settings which you need to follow up with the UberMenu addon developer or wherever you purchased the addon.
This is not related directly to the answer, but as you are using the Pro theme, you can use the Pro Header Builder to implement the sticky functionality. The Bar element in the header builder does have the sticky option. For more information: