"servers unavailable"

Well servers seem available to me. Have you tried all the steps in this FAQ support.garmin.com/.../

Yes, I have gone through all those steps twice.

Then you'll need to call Product Support for help 

update: I just gave up on waiting for support and returned the device as it appeared to have an issue as all my other garmin devices work just fine on garmin express.

Same for me. Got a new device vivoactive 4s and I get the same error "servers unavailable". I'm able to add my other garmin devices. When I connect the 4s to the latest version of Garmin Express 7.13.1.0 it displays the the unit ID and serial number in the same way it does for my other garmin devices, just without the image of the 4s and the server unavailable message so I cannot continue to register my new device or sync to garmin connect. A support agent mentioned they "couldn't locate my serial number/unit ID" then said they are still investigating and I haven't heard anything back yet. Quite annoying to have a open support chat window for a long time and then no support ticket/reference number or log of the chat even happening so how do I get feedback on my issue? I have had garmin devices for years and this is the first time I have had so much trouble just trying to connect a new device out the box. 

I've been going back and forth with product support for 2 days.  It's not just Express not working all of a sudden, inreach sync stopped working as well -- I used both of these programs within the last month.  Garmin support's final assessment for me was that 'garmin express isn't intended to work on fixed wireless internet.'  No explanation why this is a problem now when it's all been working fine for 3.5 years (same equipment, same internet, same security, etc.).  Curiously, on Chrome and Edge today, I can't even access garmin.com -- 'insecure' messages.  I can access on Firefox.  I got support from Norton and they say it's not their software blocking access to garmin servers. 

Please please please help!!!

I have been receiving the same error for over a week now, after 7 years of otherwise reasonably consistent normal syncing.

My forerunner 305 and my forerunner 310xt are unusable, after suddenly becoming rejected a week ago.

I have uninstalled and reinstalled many different versions of express, followed the advise of all the different forums, and garmin guides. Deleted all fit and htm files etc etc .Internet is fine, firewalls down, latest versions of software, time settings correct......

The devices are recognized in express, but after signing in I consistently get the message above.

Could it be a PC setting? I feel like I have tried everything, over many days, and am now getting very sad, particularly that I can't upload my IM 70.3 course to go and practice tomorrow.

support.garmin.com/.../

Many thanks for the reply. Unfortunately, I have been through this page a thousand times, for more than a week, and am no further towards a solution.

Then you'll need to call Product Support so they can investigate 

Any chance you are running a VPN?