@Sabrina apologies for the delay in the response. Are you still facing this issue? Are you getting any specific error(s)?
a few things you can try:
- using a different browser,
- verifying that your domain is correctly configured in your domain provider's website
- waiting for a few more minutes. It can take up to 6-8 hours for the managed certificate to be created
- deleting the certificate and creating a new one
- following this Azure troubleshooting documentation guide for more insight: https://learn.microsoft.com/en-us/azure/app-service/troubleshoot-domain-ssl-certificates