When you have very strict network security policies, you might not be able to access all of the domains that are needed to run Hi-Def Signage. Most likely this is affected by .biz domains simply being flagged as suspicious all together and/or the fact that our servers are located in the EU.
To use Hi-Def Signage correctly, you need to make sure your network settings allow access to our servers.
Your network needs to allow access to at least the following domains:
Hi-Def Signage servers are located in the EU. The primary reason for this is that privacy laws are more strict in the EU, which is important to several of our customers. This means that if you have any region restrictions in your network settings, then access to the EU region needs to be granted for the domains mentioned above.
When you're using ChromeOS, Google has a list of domains that need to be accessible as well. This list can be found here.