This problem seems to be intermittent. Yesterday I couldn't open the manager now I can so I don't know what it is. It was the same over the weekend it opened and then next day didn't. I've tried this on several browsers to see if that was the problem but it wasn't.
When it doesn't work. I open the manager and the screen opens to all the headings, Home, calendar, etc. But there is no calendar on the screen and none of the icons work.
I also have a problem with the workout blender which I've requested help for in the Workout Blender forum. Still waiting for help on that front.
I hope this gives you some inclination as to what the problem could be.
Lesly