Surface Pro 4, ESU: Registration fails without any error

hi Detlef_Huss​ here is my view, the “Registering for extended security support” window closing with no error usually points to a missing prerequisite or a silent activation issue. A few quick things to check:

Update everything first – make sure all latest Windows updates and the ESU preparation package are installed.

Network access – confirm your device can reach Microsoft activation servers (no proxy or firewall blocks).

Re-enter ESU key – open PowerShell as admin and run:

slmgr /ipk <your-ESU-key>

slmgr /ato

Check Event Viewer under Applications and Services Logs → Microsoft → Windows → Security-SPP for activation errors.

Restart and retry registration — sometimes it completes only after the next update cycle.