Hi @Alok Prakash Adhao • Thank you for reaching out.
It looks like you a trying to register a custom domain with setting a TXT record in the public facing DNS. From what I can see when trying to resolve the DNS settings look correctly set.
A very common cause for this happening is that the custom domain is already registered in a different tenant, a domain can only registered to exactly 1 tenant and not in multiple tenants.
You can use the OIDC endpoint to test for your particular domain for this, I have already filled in the domain you are looking for: https://login.microsoftonline.com/casacloud.com/.well-known/openid-configuration
If you load that page you will see it returns data, which to me means you either were already able to resolve the issue in which case it would be great if you could share feedback on how you resolved the problem.
If you are still facing the problem, then the page loading data tells you the root cause, your custom domain is already registered in a different tenant which is why the validation is failing, since this can only be by someone who has access to the DNS server it is most likely someone in your organization, the token URL includes the tenant ID which may be helpful for further investigation internally to see in which tenant the domain name is utilized and if it can be freed from that tenant for your use or if a child domain should be used in your case.
Should this not lead to resolution then Marti gave you the correct steps indeed to approach your Microsoft Support for further details if necessary.
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