SSD boots, but when I plug my HDD in, it doesn’t boot

Hey guys so I just bought a new Samsung 970 EVO plus ssd

and I wanna use it too boot my pc and stuff. Anyways I installed windows on the ssd and made it my boot drive. Anyways, when I plug my original HDD back in too use as a storage drive, the PC doesn’t boot at all, it recognises it in the BIOS, but can’t boot onto my SSD.

But, when I unplug the HDD and boot up again, it boots perfectly. I don’t know why it’s doing this but the SDD & HDD do not work together. Anyways have any help?