Thanks for asking question! To connect via FTP, you need the following information-
• The FTP host name: which will be something like waws-prod-blu-001.ftp.azurewebsites.windows.net (the blu token might instead be am2 or db3 based on location). You'll find it under the Dashboard tab for your site in the Azure portal.
• Your username: you'll also find it on the dashboard, under Deployment User. It's the same as your git username, but prefixed with the site name. To add to this since user-level credentials are linked to the user and not a specific resource, the username must be in this format (<app-name>\<user-name>) to direct the sign-in action to the right app endpoint.
• Your password: use the same password as when you git push, Also note Azure does not show your user-level deployment password. If you forget the password, you can reset your credentials.
Also verify if you are using the correct FTP endpoint from the Portal -> Overview blade; you may double check on network level restrictions not blocking the communication between Azure and the FTP client.
You may refer to below doc links for more details on this:
https://github.com/projectkudu/kudu/wiki/Deployment-credentials#important-note-about-the-ftp-username
https://github.com/projectkudu/kudu/wiki/Accessing-files-via-ftp
Let me know if issue persists.