Queena You're likely missing a prerequisite update and restart.
The following steps must be completed before installing and activating ESU keys:
- Install the following SHA-2 code signing support update and the following servicing stack update (SSU):
Windows 7 Service Pack 1 (SP1) and Windows Server 2008 R2 SP1:
Servicing stack update for Windows 7 SP1 and Windows Server 2008 R2 SP1: March 12, 2019 (KB4490628)
and
SHA-2 code signing support update for Windows Server 2008 R2, Windows 7, and Windows Server 2008: September 23, 2019 (KB4474419)
2. Reboot.
3. Install the SSU listed below (or a later SSU) and the ESU licensing preparation package:
Windows 7 SP1 and Windows Server 2008 R2 SP1
Servicing stack update for Windows 7 SP1 and Server 2008 R2 SP1: January 14, 2020 (KB4536952)
and
Extended Security Updates (ESU) Licensing Preparation Package (KB4538483)
4. Reboot.
5. Install and activate the key.