Hi Sandi,
What version of the data model are you using? If you are using 10.1 then you will need to make the changes that I noted in the above post. Or if you are just putting your data into the MPK that was provided above it should work.
In your post you mentioned you have relationships within the data model to support comments. The 10.2 version of the application (what you grabbed on Github)handles relationships in the code (JSON) not in the data model or mxd. So, within the parks.mxd you should not have a join to the comment table, if you are using the configuration the way it was on github.
Hope this helps,
Lindsay