Why am I not able to select Product in Service Desk?

Now, as your Service Desk is configured, you proceed to register a new user or to login. However, as you try to submit your first Issue, it might come as a surprise that your Product drop-down list is empty:

There are three possible reasons for that:

1. The "Product" checkbox is unchecked in your Project settings

The most common case is than none of the Projects are marked as "Product" to be displayed in Service Desk. The fastest way to check that is to go to the Projects and Custom Fields tab in Service Desk settings, and checking the Projects you want to be available:

Alternatively, you can check "Product" from the Project details page in Targetprocess. If it’s checked, Service Desk users are able to submit their Requests for this Project. Open your Project card and click the 'Is Product?' checkbox in the right panel:

2. Bad Company-Project relation

If you have selected some Company for this project, only Requesters from this Company will be able to see it in their Help Desk. Either remove the Company from Project properties, or add Requesters to the Company. More details are here.

3. Help Desk practice is disabled for your process

Please check Settings → Processes → [Your Process] → Practices and see if the Help Desk practice is checked:

Read more about practices here.