Hi @AlexP-0099,
Since you have already added the TXT record to the sites DNS provider manually, you might be experiencing a DNS propagation delay.
According to this documentation, you can try this alternative:
you can use the HTML webpage method to manually verify your domain. This method allows the certificate authority to confirm the domain ownership of the domain that the certificate is issued for.
-Create an HTML file that's named {domain verification token}.html. The content of this file should be the value of domain verification token.
-Upload this file at the root of the web server that's hosting your domain.
-Select Refresh to check the certificate status. It might take a few minutes for verification to finish.
For example, if you're buying a standard certificate for azure.com with the domain verification token 1234abcd, a web request made to https://azure.com/1234abcd.html should return 1234abcd.
Hope that helps. Let us know if you have further questions.
Thanks,
Grace