Before any investigation to understand why users are getting errors, it is imperative for users to produce an exact and exhaustive copy of the error message (either from BigQuery/Tableau/Dataiku/Qlik etc). Most of the time, the reason is indicated in the error message.
Most errors will undoubtedly be related to inadequate permissions, either on the user side, or on the "server" side, or that the query itself is malformed. Carefully examining the error will, in most cases, explain what the problem is.
In case of permission errors, it's necessary to verify the that the user is present in a group authorized to have access to the Data Product Project. Normally the project manager is responsible for this verification.
Additionally, it may be that the user is querying a table or view in a dataset isn't shared with the group that the user is a member. In this case, the dataset must be shared with the corresponding user group.