Make sure that you are authenticated to Office 365. To do this, follow these steps:
1. Sign in to the SharePoint Online site by using your Office 365 credentials, and make sure that you click to select the Keep me signed in check box.
2. Open a document library in Explorer View.
3. Try to access the mapped network drive.
If you are authenticated to Office 365 and the issue persists, make sure that an entry for SharePoint is added to the Trusted sites zone in Windows Internet Explorer. To do this, follow these steps:
1. On the Tools menu In Internet Explorer, click Internet options.
2. Click the Security tab, click the Trusted sites zone, and then click Sites.
3. Verify that the following entries are listed in the Websites list:
4 If these entries are not present, add them to the Trusted sites list of websites.
5 Click the Local intranet zone, click Sites, and then click Advanced.
6 Verify that the following entries are listed in the Websites list:
7 If these entries are not present, add them to the Local intranet zone list of websites.
Volg de stappen die in onderstaande url staan: