I've been slowly buying parts to deck out a beat up iPod 5.5 I got on eBay, and I finally got everything. I decided to first replace the hard drive, but it's been giving me a headache for 4 hours now.

I have a single 256gb amazon basics SD card in there, which could be the problem, but no other SD card I've tested has worked either. I have to force it to go into disk mode, it takes at least a minute every time, and it's not completely consistent either. It usually defaults to the apple support screen and then to the very low battery screen. When I do get it into disk mode, I plug it into my PC, and I get a connection sound, but it's not detected in iTunes, file explorer, or disk management. It is detected in device manager; I found a thread that said to uninstall the iPod through there, but it didn't do anything. Additionally, the iPod shuts off and reboots after about a minute when in disk mode. This has been much the same experience when plugging it into a mac. With the original hard drive, it worked perfectly, bar some weird issues with the battery, which is pretty weak, but it seems to do fine with enough charge. I'm at a total loss here. If anyone has any advice or fixes, it would be much appreciated.