A Site ID is a unique identifier that distinguishes a running instance of Issuetrak from all others. Additionally, it is used to distinguish production sites from test sites: Production sites and test sites require different site IDs.
You will be prompted to enter a numeric Site ID when you deploy a new instance of Issuetrak or upgrade an existing instance from a version (less than 15.2) that didn't require it. If you do not know your Site ID, then please reach out to Issuetrak Support so that we can provide it to you.
If you have already upgraded to Issuetrak 15.2 or above, then you can find your Site ID in your site by navigating to the License Key screen or clicking on the question mark towards the top-right area of the screen and then choosing About Issuetrak.