Cloned my laptop’s HDD to a new SSD. Now it won’t work unless my old HDD is connected externally

Using Macrium Reflect, I cloned my 2TB HDD to a new 500GB SSD. After installing the new drive, I got hit with “no bootable devices found”.

I ran Macrium’s rescue media to try and resolve boot problems, but it didn’t fix anything. I could only get my laptop to boot again with the new SSD when I plugged in my old HDD thru USB and used it as an entry point to the Windows Recovery Environment. From there I used this answer to fix the issue:

I know now with 100% certainty that my laptop’s using its new SSD when it’s booted up. But here’s the issue: the moment I unplug the old HDD, my laptop immediately bluescreens with error INACCESSIBLE_BOOT_DEVICE, and won’t boot again until I plug it back in.

I feel like there’s something easy that I’m missing here.