Notebook Hardware and Upgrade Questions

My battery died with 0% life. The power charger evidently died with it, too because it does not work with my new battery. I have a new OEM HP BP02XL battery with the same specs, and  new OEM HP charger with same specs. I don't like that the battery is internal vs external. After removing the cover which is delicate, and carefully put in new battery, I am faced with an icon showing "no battery detected" and "unknown remaining" when I remove the power cord.  It seems this is common with many laptops, mostly HP. My other laptop had an external battery and I had no problem replacing it.  I've done so many things that I read was suupposed to rectify this and nothing is working. Diagnostics shows charger is there, but battery is missing. The battery does read that itis100% charged. I charged it for almost 36 hours before I started the laptop. I am using the laptop now, but I have to keep the power charger in otherwise it shuts down. I haven't read anywhere that possibly the battery cable could need replacing or could be bad and could that cause this?  I carefully removed it and replaced it. I really  don't know what to do. Has anyone done a full reset of your laptop to factory condition and has that worked? I thought of reinstalling Windows 10.  The updates are current. I need to get this fixed because the vendor wants the battery back if I can't use it. Honestly, I don't think it's the battery. The fan is working. Everything is fine execpt this "battery not detected" message. Any ideas that worked for you?