I bought a tablet at the end of 2017 I did a factory reset because I'm selling it well now it will not let me access anything on the internet. No Google, Play Store, email, or Gmail. I'm trying to find out how do I find my activation code that would have been on my receipt and I don't have my receipt???
OK I think I misread part of that. However, if you are clearing off the tablet to sell, then why would you be on it trying to get on the internet? You can only use a device if you have the information for the original account. If you don't have that info in the device, you can't use it. An activation code isn't needed at that point.
If you are selling it and enter your email and password into the device as required, then it will still be there when you sell it.
Now if you can't remember the email and password for the account attached to that device, we can't help with that.