Recently we saw an issue with a customer whose dashboard was not syncing on a regular interval. And it would frequently display the lightning bolt in the Gauge footer on the dashboard. See image below.
When you see this lightning bolt, this simply means the browser is unable to connect to our server that fires off the automatic syncing for your dashboard. Please note, this is a different connection than what we use when we sync to your actual data. This connectivity is a simple browser connection used to notify the browser about sync events (when to start, when its finished, when it can't). It uses a technology called WebSockets that is commonly used in many web applications.
If you are seeing the lightning bolt, it usually means you are not connected to the internet. A quick refresh of the browser can clear up any obvious or simple connection issues. 9 out of 10 times that does the trick as the Internet is a finicky friend.
In the odd case that is not it, we recently found Advanced Firewall solutions may end up blocking WebSockets traffic from leaving the network. This is super rare as so many software solutions use sockets. If you are pulling out your hair on why you are seeing the lightning in one office but can easily connect from another location, its probably the firewall. The occurrence we saw recently was a firewall with Deep Packet Inspection turned on for certain users.
It's best to ask your network administrator what they can do for your situation. Every firewall is slightly different so they would know best. If we can help, please let us know!