Problem

Since the September 2016 release, when Tridion was activated, you could have the "new page" button disabled, making impossible to create any page.

Example:

Syensqo IS - Customer Support > "New page" button disabled > image2016-9-14 10:45:7.png

Solution

Keeping Tridion active, browse again to your page. .

From a Solvay ONE space home page, click the space banner:

Syensqo IS - Customer Support > "New page" button disabled > image2016-9-14 10:54:40.png

From any other site, use the navigation (top or left menu) to access your page again:

Syensqo IS - Customer Support > "New page" button disabled > image2016-9-14 10:55:59.png