Temporarily disable any third-party software that might be interfering with the activation process, such as antivirus programs or firewalls. Try activating Windows 7 again.

net start sppsvc

Corrupted Windows system files can break the activation UI. Even though Windows 7 doesn’t have DISM natively, it does have System File Checker.

Change the to Automatic (Delayed Start) and click Start if the service is stopped. Registry and Command-Line Repairs

If the service restart didn't work, you can force Windows to re-evaluate its licensing status using the Windows Software Licensing Management Tool (slmgr). Open the Command Prompt as an Administrator. Type slmgr /rearm and press Enter.