Hi, I had this issue as well - the fix for me was to change the work hours from Outlook on the web, as the Outlook desktop client is currently broken, with the inability to save work hours.
Click the gear wheel, then choose Calendar, work hours and location, and change the start time to 9am (or whatever time you start). When you change this, it will give you the option to save, and then after a few minutes restart outlook desktop and it will work.
Hei Aaron
I tried your solution as it seems to have worked for several people, but unfortunately it didn't work for me.
What I did was changing "start" and "end" hours on the web version to see if they updated on my desktop version and it worked so that the greyed-out hours coincide, but it's still so that every time I open the Calendar tab on Outlook, it shows the days starting at 00:00 and I have to scroll down to see anything on my calendar.
This was the issue the others were reporting, and found your suggestion to be the solution, right? Or am I misunderstanding here?