Launch Powershell (note, it is not Command Prompt, but Powershell), and run this code to see if you have an OEM license on the motherboard. If it doesn't return a key at all, then it means they lie to you about having a key on the motherboard.
(Get-CimInstance -ClassName SoftwareLicensingService -Property OA3xOriginalProductKey).OA3xOriginalProductKey
If it does return a key, go to the Store app, download a free app called ShowKey Plus, use the Check Edition feature, input the key, and check to see what edition the key is for. Let me know what it says.