The Microsoft 365 license tokens should be activated each 3 months on RDSH Servers (Windows Server 2012 R2). When trying to activate the Microsoft 365 apps, there is the following error message: “Sorry, there was a problem while trying to connect to your account. Error code 0x15”. When starting an Office app, Word for example in Safe mode, the activation is successfull. Even after disabling all add-ins the issue exists. Single Sign On is used. The accounts are On prem and are synced through AD Connect tool. There is no Hybrid configuration. The issue started since beginning of this year.