No Internet connection available or network connectivity degradation.
Verify the “PAC” configuration:
Not all the networks infrastructures are setup in the same way. The PAC configuration defines how web browsers and other software’s (Like Outlook) choose the proxy server assigned to them. In this context the PAC setup (Proxy Auto Config) is the primary network check to carry out in order to make sure that we are compliant to the corporate network policies and configuration.
Open Internet Explorer, Tools >> Internet Options >> Connections >> Lan Settings >> verify PAC configuration:
Check if your network infrastructure relies on a proxy server; If the configuration looks ok and compliant, try to open any Internet page to check if Internet is working;
If you cannot connect to Internet, verify if you can access to another network resource like a Network share.
If you cannot access to any network resource, there might be an issue with:
Network Interface card
Internet Service Provider
O365 Service Health
1. Sign in with your Office 365 admin account at https://login.microsoftonline.com
2. In the Office 365 admin center, go to Health > Service health.
The site provides a comprehensive picture about the known issues and maintenance activities in progress on the platform for each one of the O365 environments.
It’s a good habit to always keep it at hand: it might spare long (and worthless) troubleshooting sessions to pin point a problem which is actually occurring at server level.
Red, green or yellow status for any O365 environment allow to check if there is any DNS know problem or any work in progress on the area you are performing the troubleshooting.