Series 2 Watch can’t be updated?

I’ve purchased a used Apple Watch 2 (42mm) and I am unable to pair it to my iPhone 8. It says the watch software is out of date, but as soon as it attempts the update from the phone app, it says “Pairing Failed: Your Apple Watch couldn’t pair with your iPhone.” It then unpairs from the phone.

At the top of the article, it states that the newest software update is compatible with the Series 3 and above. How do I pair my 2 with my phone without updating the software?