The report is invalid. Are you using My Domains or matrix style reports?
Issue
If permissions to the reports are granted, sharing settings to the folder are set, and it is not a matrix style report and users still see this error, it is likely that they have High assurance session required enabled in their Salesforce org under Access Policies.
Workaround
Disable the High assurance session required policy in . Use Conga Queries, which are unaffected by this Access Policy.
