Yes, you do need to upgrade your subscription to use latest versions of Aspose.Cells for .NET to eliminate evaluation warning sheet and to work with the component with full capacity.
I think your license “Aspose.Total.lic” might be expired to use the latest versions/fixes of Aspose.Cells for .NET. For your information, any of the fixes / new releases will work fine unless your license is not expired (license expiry date can be seen in the license file opening the license file into notepad). You may use our latest versions 4.8.1.x if your subscription allows this, you may open your license file into notepad and check the expiry date. When you purchase the license, you are eligible to use versions / bug fixes of the products that are released in the next whole year. But if a version/fix is released after your subscription expiry, you need to upgrade your subscription then.
Have a good day!