We created an asp.net core webapp hosted as Azure App Service with app service authentication. In App Studio we set up a personal tab and distributed the app as enterprise app. For all users the app is working without problems in the Teams Web App, but for some users it's not working in the desktop app. If those users use the app the tab does not display anything.
We tried to cleanup the Teams App and also re-installed the Teams Desktop App but with no success. The log in Azure shows only one entry if the user tries to connect the custom app (XXXX is blanked out hosted web app):

2020-07-29T06:33:46 PID[32324] Information Redirecting: https://login.windows.net/78dbf809-648b-40d8-a0a1-17249b3065ca/oauth2/authorize?responsetype=idtoken&redirecturi=https%3A%2F%2FXXXXXX.azurewebsites.net%2F.auth%2Flogin%2Faad%2Fcallback&clientid=b93bdff9-599c-458a-9d5f-86f0e4a51225&scope=openid+profile+email&responsemode=formpost&nonce=919fd712db1b4da9a1ca92c6eaf7ffd2_20200729063846&state=redir%3D%252F

Users with a working app do not get this entry. As soon as we switch off authentication, the app starts working.