Welcome Raman Jathar,
Thank you for reaching out to Microsoft Q&A forum.
If your Windows 8 Pro license was purchased as a retail license, it can generally be transferred to a new PC, provided it is no longer in use on the old device.
To better understand why activation is failing, could you confirm:
- Is the new PC running Windows 11 Pro or Windows 11 Home?
- Are you activating with the original Windows 8 Pro product key, or was the license previously linked to your Microsoft account?
- What is the exact activation error code or message shown in Settings > System > Activation?
As an initial check, please open Command Prompt as Administrator and run: slmgr /dli
Then let me know whether the license channel is reported as Retail or OEM.
For reference, Microsoft's guidance on reactivating Windows after a hardware change is available here:
Transferring Windows Licences - Microsoft Q&A
Reactivating Windows after a hardware change | Microsoft Support
Once you provide the activation error and license type, I can suggest the next steps.
Looking for your update.