Offline message will not allow SketchUp to open
This is an issue where the network is blocking access. Sometimes you can test this by tethering to a phone to see if the sign-in works. If that works, it shows that something on the network is causing the issue. Or if it is a laptop, users can go to a local coffee shop and try, again, bypassing the network they are on.
Here are the things they need to check:
SketchUp requires uninterrupted access to the internet for features such as the 3D Warehouse, Add Location, Licensing, Extension Warehouse, and Trimble Connect. To ensure connectivity, you may need to adjust settings in your Firewall, Proxy, VPN, ad block, DNS, or Internet Security software for your network or computer. We also recommend accessing the 3D Warehouse through the built-in 3D Warehouse Browser and/or your web browser (https://3dwarehouse.sketchup.com/) instead of the component browser.
SketchUp needs access to the following ports:
Subscription Licenses: 80, 8888, and 443
Network Licenses: 5053, 50530
SketchUp needs permission to visit all of the sub-domains for SketchUp.com, Trimble.com, and Trimblepaas.com easily included as:
To check if the computer is connected to the Internet, SketchUp tries to contact www.bing.com. This default can be changed if you do not wish to whitelist bing.com.
Trimble uses OneTrust (cdn.cookielaw.org) to manage cookie banners. If this site is blocked, Trimble sites may not fully load.
Please see this article for the complete description and list of steps to take to correct the problem of connecting to the Internet through SketchUp Pro, as well as steps to change the default test URL: http://help.sketchup.com/en/article/3000056