Windows 10 can't upgrade

Okay, so I bought my new Acer Aspire E14 E5-411 laptop. 

But, an issue I'm facing is, I can't upgrade it to Windows 10. 

Here's how it started: 

I booted up the PC, I configured all my settings, data, etc. like a normal first-time boot. Then it asked me if I wanted to upgrade to Windows 10, and that if I said no now, I would always have the ability to do it whenever. So, later that day(yesterday as of now), I started upgrading to Windows 10. It then told me, "Hey! We kinda need your product key for WIndow 8.1 for you to do that." So, I panicked, I looked through all the papers that followed, I looked at every nook and cranny on the laptop, but nothing. So, I searched it up on Google, which lead me to believe, I should've accepted it the first time, and that I should reset it to factory settings, so I could redo the whole thing. So, I did. Then as I was upgrading, it told me, "Hey! If you upgrade now, you'll need a Windows 10 product key before getting a full version of the OS. 

So, what gives? It says on a sticker plastered on top of the box it came in, and even on laptop itself that I get a free copy of Windows 10. But, nope! None of that! 

Please help me, because I have no idea what to do.