Is this Internet Explorer? If yes, please close it and use Chrome or Firefox.
Alternatively, try this (from the help page):
Add the hub site as a trusted site in Internet Explorer.
Do the following:
In Internet Explorer, open Tools > Internet options.
Select the Security tab.
Click on Trusted sites.
Click on Sites.
Enter the website address for the hub in the text field and click Add.
Click Close.
Refresh the browser window.
vizmind.eu