Sitecore 9.1 Initial Release with Identify Server User Boost Feature Patch
If you noticed Sitecore user boost feature doesn’t work with your Sitecore 9.1 Initial Release with Identify server, request a patch from Sitecore support with the reference number: 308082.
Please make sure only to proceed for this particular Sitecore version. The patch contains only Sitecore.Owin.Authentication.dll and Sitecore.Owin.Authentication.config 2 files.
Interestingly in the 9.1 Update 1 version that’s just released, didn’t see this reference number in Release Notes: https://dev.sitecore.net/Downloads/Sitecore%20Experience%20Platform/91/Sitecore%20Experience%20Platform%2091%20Update1/Release%20Notes, maybe didn’t make it in time for QA.