If you passed GH-300 but cannot see the certification in your Microsoft Learn profile, first make sure you are signed in with the same Microsoft account associated with your certification/exam profile. Microsoft’s GH-300 study guide specifically notes that connecting your certification profile to Microsoft Learn allows you to share and print certificates.
You can check the official GitHub Copilot certification page here: GitHub Copilot certification
If the certification is still missing, this would be an issue with the certification/profile record rather than the GH-300 training course itself.