You installed the game somewhere Heroic can't access. By default, Heroic can only access (11:46:57) [INFO]: Installed in: /run/user/1000/doc/f676a22e/HogwartsLegacy
~/Games/Heroic/, /mnt and /run/media. Either adjust its permissions (using the Flatpak permission manager in the KDE system settings, Flatseal, or the Flatpak CLI), or move the game to one of those folders. After that, open the 3-dot menu on the game details page, select "Change install path", and re-select the install path