Urgent! The custom domain doesn't work at all

Hi there!
I specified my domain settings in Backendless ones: web.guitarability.com
CNAME is develop.backendless.com in my domain settings themselves.
When users sign up, they see this link: http://web.guitarability.com/api/users/confirmation/F5ECDD656811F983B13B2144374AF8D2707A263828AD0A253645AEBA0F04AFD6
When clicking it, another page is opened:
WHY is it happening?

Hello, Evgeny!

Please, provide your application id.

Hi, Application ID: A649A321-BF0E-DC5E-FF3C-1BF7ADC6E000

Unfortunately, we cannot reproduce your issue.
Here is the use-case we’ve tried with:

  1. Call “register” method for a new user:
curl \
-H application-id:APP_ID \
-H secret-key:SECRET_KEY \
-H Content-Type:application/json \
-H application-type:REST \
-v http://DOMAIN_NAME/api/VERSION/users/register \
-d '{"email":"SOME_VALID_EMAIL", "password":"pswd", ....other required fields}'
  1. Wait until confirmation email comes
  2. Follow the confirmation link
    Please, try these steps for your app. If it doesn’t work - please provide your concrete steps to reproduce this issue.