Problems with my Dual Boot after Installation

Hey erverybody, i switched from Nobara to Bazzite to couple of days ago.
I have Bazzite on my NVME and have a Win10 Installation on a Old SSD in my Case.
With nobara i always had the option to boot in nobara or in win10. now this option just disappeared.
Bazzite sees the device, but i cant start from it.