Flatpak Desktray Icons

I have three different Flatpak images running on Ubuntu Budgie, which are Remmina, Clementine Music Player and Strawberry Music Player. When they are open, they icons do not show up on the desktop tray properly. instead what I get is something that looks more like a red stop sign as though it cannot find the icon to load. I only get this problem with the Flatpaks. Does anyone have any idea on how to fix this please?