Hi, we have been using Planner to control project folder access for about 3 years now and find it very useful. We set up a new project as a separate Planner site and add the users for that project. Today at least two of the Planner sites (two different projects) will not allow anyone access. The user can select the site and is taken to the site Planner homepage. From there we select the files option from within the ... sign. The new page loads and then the user is redirected to a page that states you don't have access. There is an option to request access. If pressed the user receives an email telling them they now have access but they don't.
We have tried the faulty sites on IE, Edge and Firefox and they all display the same issue.
We have not made any changes to the problem sites.
If we type in the URL into file explorer (as if we had selected view files in explorer in IE) we can access the files. If we navigate via One Drive from Edge we can access the file.
It is as if from within a browser the authentication link is broken.