I had built a Conga Query that exploited the Product2 relationship from the OpportunityLineItem. Yet, when I used this in a Conga Composer URL, I got this error:

INVALID_FIELD: No such relation 'Product2' on entity 'OpportunityLineItem'

I know that the Product2 relationship from OpportunityLineItem was added by SFDC in V30

yet my Conga Composer URL was V33:

&serverUrl=https://mydomain.my.salesforce.com/services/Soap/u/33.0/someId

So, what gives?

Per Conga Support, the serverUrl is used by Conga solely for determining the instance name and they smash the rest of the URL with V29 (!%!).

Of course, this could change in the future so, hopefully, this post will become obsolete.

Workaround
Instead of using the OpportunityLineItem.Product2 relationship, you can fallback to the OpportunityLineItem.PricebookEntry.Product2 relationship. I don’t know what I would do were I needed a Conga Query on Order – an SObject introduced in V30