Follow one of the quick start/how-to guides I uploaded my custom html (wingtips) file to blob storage.
https://mystorage.blob.core.windows.net/b2cpages/unified.html
I then tested that I was able to access the page through a web browser with success.
I then configured the tenant signin/signup policy to use the custom page and the tenant is returning a 404. (using all defaults the tenant works fine)
Any suggestions? If you need additional details just comment and I will update.
Thanks, Chris