Flatpaks are not showing in the Kickoff menu in KDE

This happens when I try to install a flatpak. For example, let’s say I want to install the retroarch flatpak (The official repos version doesn’t work last time I tried.) I install it and then it does not show in the Kickoff menu. Please help.

Stupid question, but have you rebooted since installing flatpak? I know the menu integrations don’t work (at least for me) until I’ve rebooted.

I have. It still doesn’t work. Sorry for responding late.