The browser you're using does not support website redirect or the website domain is not under trusted website. Please add the website into the trusted sites for verification. Below are the steps of adding trusted site.

  1. Click on Start.
  2. Type inetcpl.cpl, and then press Enter.
  3. Internet Properties window will open. Select Security tab.
  4. Under Trusted Sites, click on Sites button.
  5. In the Add this website to the zone box, type in the website that your browser just opened when verifying the account and then click Add.
  6. Click on Close button.
After the trusted site is successfully added, close Microsoft Edge and reopen the browser. You may back up your data to cloud service now.
If you still encounter any issues, please contact Synology support for assistance.