The only other things that I added to affect the frame were a UIGridLayout and a UIPadding. All of the other frames and buttons and such rounded when I added UICorner.
What solutions have I tried so far? I have tried to increase the radius of the UICorner, but it had no effect. I also tried to delete the UIPadding and the UIGridLayout, but that just made the whole GUI look worse.
I tried the same thing, it seems like the UICorner does not work on ScrollingFrames (yet). Maybe this is yet to be added because the UICorner is still in beta?
More information on UICorner’s effects on ScrollingFrame and the plan to support them at a later date were posted in the initial announcement of UICorner;
For anyone still wondering, this is still not possible.
My simple solution is to just have a rounded frame with a scolling frame inside. The scrolling frame just needs to have an invisible background.