Yes, there are logs via the Activity Log button on your Dashboard, and then there are settings in the logs to switch to Verbose mode for richer logs.
The logs may or many not show something of use depending on the case. I expect it will most likely confirm that the endpoint was not found/timed-out and the call was then send to voicemail, but it will not necessarily tell you why this happened. For that, you will need to be able to analyze network traffic, and have some knowledge of SIP (hence why I recommended a Partner in this case).
As for "serious money" that really depends on your perspective and what you value most:
1) "I'm a business and I need my phones up ASAP!" => Definitely use a partner, you pay and you get a service
2) "I just want to learn how to use the system, I'm not in a hurry" => Do the Academy course, and ask questions in the forums as you go. Look on the right column of this forum and sign up for upcoming free Webinars with our trainer.
So it comes down to making a decision at this point I think, and whichever way you choose we can help accordingly, but the forums are not meant to provide commercial grade support.