YouMail works by forwarding your voicemails to your Deposit Number that is assigned to your account. We use your Deposit Number to collect all of your voicemails so you can do awesome things with them (like change your voicemail greeting and save voicemail's audio file to your computer).
Although your calls are forwarding to YouMail, they may be forwarding to the wrong Deposit Number which is preventing you from using our app and all that it has to offer.
To know for sure, test call your phone from another phone or have someone test call your phone and let you know what message plays. If what is heard is "This number is no longer in service. Error Code DID1. Good Bye". That error message means it's forwarding to the wrong forwarding number.