Specs:

• HP Pavilion 15-cw1xxx with AMD Ryzen 7 3700U
• Toshiba internal 250GB SSD (Windows)
• WD Elements 2TB external HDD (Arch)

This issue just started yesterday. I am using an HP Pavilion laptop with Arch booting from an external HDD plugged in to USB (I know there is a specific forum for laptops, but felt this one was more relevant to the issue).

Lately, I had been receiving HP warning messages during boot warning me that the integrity of my battery is worsening. Up until now, this hasn't been an issue. I would just hit Enter to continue on to boot and everything would boot into Arch just fine (yeah, I know, I should get a new battery). Yesterday, for whatever reason, I can't get it to boot into Arch. I get the exact same battery error, but when I click Enter, instead of booting, the "Welcome to GRUB" screen flashes for a second, then the laptop essentially reboots itself and ends up looping through all of that over. If I adjust it to boot to Windows, it boots just fine.

I have tried a few things to figure out what is going on:

• First I tried booting with the battery removed and just using main power to bypass the battery warning, which I figured may be causing boot issues for some reason. This got rid of the battery warning, but then I began experiencing a new issue. Arch still would not load first even though I had it set up as such in my boot order. If I manually selected to boot into Arch, I would get an error saying "Selected boot image did not authenticate", which I don't understand because literally nothing changed with my HDD/Arch install since the last time I was able to log into it.
• After doing some digging around, I found this post saying that, to solve the above issue, I could disable secure boot and I should be good to go. Which I didn't understand because I never had to disable secure boot before and I could boot into the exact same Arch install just fine, but I gave it a try
• Unfortunately, after disabling secure boot, I was right back to the original problem: try to boot into Arch, get Grub for 1 second, PC restarts and loops through the same process

At this point I'm not sure what to do. I've tried using WSL 2 to at the very least get access to important files I have on my Arch install, but that has been a disaster. No matter what I do, WSL refuses to mount the HDD, saying that's only possible with WSL 2, which is what I installed. But that's a different and irrelevant issue.

I guess what I'm looking for is either A.) help with figuring out how to get Grub to actually load, and/or B.) advice on other ways I can access the files on the Arch install on my HDD.

Thanks!