yesterday morning (GMT) I receaved the firmware update on my Lumia 950.
I have a vivoactive HR with GCM 184.108.40.206.
Until yesterday only sincronization worked and not always...
After rebooting phone when udate was finished...notifications begin to work!
Now I'm regulary receaving notifications from email, SMS, calls, Telegram (I dont' use WA)...realy amazing!
Find my Phone, Play Music and Weather widgets work very well also!
No need to reinstall GCM. I was astonished!
Now I'm very interested to see how long it will work.