As a security measure, each time you access your account after a period of inactivity, from a different IP address, device, or web browser; you will receive an email about an unrecognized device.
What is an unrecognized device?
Unrecognized device just means something is different about the way you accessed your account from the last time. It could be that you used a different device entirely to access your account or it could be something as simple as using a different IP address or web browser. The only other reason to be considered an unrecognized device is if you access your account after a period of inactivity.
What if I am using the same device as last time to access my account?
If you receive an unrecognized device email after using the same device as last time to access your account, you may disregard the email. You likely received the email because your IP address was different from the last time you accessed your account using the same device.
If you know that it was you who accessed your account, you can ignore the unrecognized device email.