Windows 7 is "end of life" and Micorsoft has dropped support of this version and does not sign drivers anymore for it.

Version 2.7.x.x of the NXDRV-WIN driver will be the last version of the driver supporting Windows 7 and only get fixes for major issues, if requested by customers.
And this version will only work when "TESTSIGNING" is activated in Windows 7.

Until Version V2.6.1.0 thre was only one NXDRV-WIN Driver version for all Windows versions (NT / 2000 / XP / 7 / 8 / 10).

This has changed because of changes in the Microsoft support of Windows versions and the handling of driver signing