Serhii-5295, we’d been waiting for your response. Adding to DavidWarwick-6573 suggestions. I understand it may be late, kindly let us know if you need further assistance.
I understand you have already verified the DNS records and investigated via Dig. You may double-check/validate the DNS records:
A. If you haven't done this already, you may leverage App Service diagnostics from Azure Portal> Navigate to your App Service app in the Azure Portal.
B. In the left navigation, click on Diagnose and solve problems
and “Availability and Performance”. Go over the highlighted (screenshot below) options- to see if it provides additional pointers. (screenshot below)
Validate the DNS records:
- For root domain (create two records): -
A
record – [example mytestsite.com] -add an A record (host =@). With app's IP address (copied from App Service WebApp ‘custom domain’ blade). Not recommended to use a CNAME record.
-TXT
record (host =asuid) Yes, as you noted App Service accessesasuid
TXT record to verify ownership of the custom domain - For sub domain,
-[example www.mytestsite.com and my.mytestsite.com] – You may add CNAME records.
Additionally,
Checkout the steps outlined in the doc to fix ‘Domain verification is not working’
Take a look at the detailed step-step instructions on : Map an existing custom DNS name to Azure App Service