I entered the one that shows under Status information in Settings as being my serial number, so I have no idea what the deal is. I have a Samsung Galaxy Tab S7+, Wi-Fi version, bought new here in the USA from Amazon itself. I was able to register my Tab S4 a few years back, and now today my new S21 Ultra, with no problem. Fwiw I'm on my S7+ as I write this, and I was on it when trying again to get my serial number accepted.
Yes. And I even tried copy and paste, which is possible to do with text within settings. I'm being told my serial number is incomplete, not wrong, and IIRC, I'm not the only person with an S7+ that this has happened to.
No zeroes or O's, and the 1's don't look like I's. But like I said, I even submitted a copy and paste, which got the same result. If you hold down on the serial number, the system says that it's been copied to clipboard.
There isn't one, I checked, this is the WiFi version, and a Google search confirms that Samsung says that its WiFi devices don't have one.