Windows won’t boot from the correct drive.

This morning when I woke upI noticed my computer was off and the power button was blinking. I assume there was a 1 second power outage overnight because this happens on occasion where I live. I start up my pc and after I put in my pin, it is as if I just set up a new computer. After some investigating, I realize that windows booted from one of my side SSDs, the one that had windows from my old pc. I now can not get it to boot from the windows on my M2 ssd, which is what my PC is built on for the past 3 years.

I have verified that the m2 is working. It is picked up as an SSD by my bios and I can access files on it like opening pictures and such. I can verify that the windows file is still there. But when I go to my BIOS it does not show up on the boot priority section. Ive also tried some of the tricks I read here. I reset my pc 5 times at least, I shut it off and unplugged it and hit the power button, etc.

Any ideas? I really don’t want to crack it open and go in because I am nervous I’ll break something. if that’s the only option I will probably bring it in to a shop or something. Thanks in advance.

Also sorry if this is tagged wrong. Wasn’t sure if it counted as hardware or software.