Hi guys, figured this out today thought I'd spread the word in case anyone is stuck on this. Mumble on iOS use to have problems for some people because they cannot obtain a certificate to certain mumble servers. The work around use to be connecting to iTunes and porting the certificate from your PC to the phone, but here is a simpler solution.
Simply download Mumble on iOS (I'm using iOS 8), add in the server you want by going into:
1. Favourite Servers
2. Click the plus (+) button at the top right
3. Enter the server information
4. Connect

At this point you will get a message asking what you want do with the server certificate, at which point you will click "Trust certificate". (NOT DONE YET)
After this go to:

1. Preferences (main menu top left)
2. Certificate (bottom)
3. Plus button (+)
4. Generate New Certificate
5. Simply type in your Mumble user name
*If you use more than one, you have add them as well.