proxmox boots in grub rescue

I‘m running proxmox itself (and the systems) on an 128GB SSD and storing the data on a 4TB HDD. Now I installed a second 4TB HDD for more storage and booted again, but proxmox booted in grub rescue and says error: disk „lvmid/……/„ not found. It recognizes all Disks with all partitions, but when I ls or cd them, i only get unknown filesystem. I also disconnected the new HDD but that didnt fix the problem. I was able to set boot, root and prefix to the partitions and paths, but afterwards, linux, boot, etc. were unknown commands. Now I‘m slowly at my wit’s end…