Gateway error: Data source access error. Please contact the gateway administrator

I get the error "Data source access error. Please contact the gateway administrator" when trying to access an Analysis Services model.

• Created a simple one table model in VSTS, added admin role with my ID (domain\id) and deployed to SSAS.
• Created a simple report in Power BI desktop and published to Power BI service.
• Added a gateway on the same server as SSAS.
• Changed the service account of server to my ID (domain\id) (also same result using the default service account)
• Ran newtwork ports test from gateway. Shows Completed (Succeeded)
• Gateway network tab shows Network status: Connected
• Manage Gateway from Power BI and added data source using my ID for credential (domain\id). It adds me as a user to the dataset using my upn (name@x.com)
• Open the report and get error: "Data source access error. Please contact the gateway administrator"
• Checked the gateway log and see:
  • DM.EnterpriseGateway Information: 0 : 2018-08-17T15:29:01.8322048Z DM.EnterpriseGateway 86e218e9-7e7a-4104-b99b-5c0cc5333e82 2aaed418-5b3d-ea02-e257-7a36be986432 MGCC 20795519-b617-4245-b13e-c32922339a97 FCF0C810 [DM.GatewayCore] Db pool opening raw database connection to [MSOLAP.5: <pi>MSOLAP.5rovider=MSOLAP.5;data source=servername;initial catalog="Gateway test";cube=Model;sspropinitappname=PowerBI;effectiveusername=name@x.com;connect timeout=60:[Windows] Encrypted Credential information omitted</pi>]
    DM.EnterpriseGateway Information: 0 : 2018-08-17T15:29:01.9103418Z DM.EnterpriseGateway 86e218e9-7e7a-4104-b99b-5c0cc5333e82 2aaed418-5b3d-ea02-e257-7a36be986432 MGCC 20795519-b617-4245-b13e-c32922339a97 850B9BB4 [DataMovement.PipeLine.GatewayDataAccess] Replace effective user name in adomd connection string from name@x.com to name@x.com.
• Reviewed troubleshooting steps from https://docs.microsoft.com/en-us/power-bi/service-gateway-onprem-tshoot
  • Confirmed effective username within the gateway logs: name@x.com
  • From server, ran "whoami /upn" and confirmed name matches: name@x.com (Name here was all lowercase, and name in log had caps for name. Tried mapping name to all lowercase and same result.)
  • Followed steps to check UPN from Azure Active Directory via Graph Explorer. Name matches: name@x.com (caps here too)
• My id (domain\id) is the service account for SSAS and is an admin on the server. Power BI Desktop report works from the server.
• Checked in registry for HKEY_CLASSES_ROOT\MSOLAP.5 and it does not exist. I have a key for HKEY_CLASSES_ROOT\MSOLAP and HKEY_CLASSES_ROOT\MSOLAP.8 but not 5.
• Gateway is Version: 14.16.6792.1 (August 2018)