Hi @Belgian Malinois,
Please help check if you have chosen this opinion in your datasource.
Please also try to grant "Allow log on locally" permissions to domain user accounts.
1.On the report server computer, in Administrative Tools, open Local Security Policy.
2.Under Security Settings, expand Local Policies, and then click User Rights Assignment.
3.In the details pane, right-click Allow log on locally and then right-click Properties.
4.Click Add User or Group.
5.Click Locations, specify a domain or other location that you want to search, and then click OK. 6.Enter the Windows account for which you want to allow interactive login, and then click OK.
7.In the Allow log on locally Properties dialog box, click OK.
8.Verify that the account you selected does not also have deny permissions: a. Right-click Deny log on locally and then right-click Properties. b. If the account is listed, select it and then click Remove.
More details please refer specify-credential-and-connection-information-for-report-data-sources
Remember to restart SSRS server and test. Hope it will be helpful.
Regards,
Zoe Hui
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