Why won't iCloud work with Outlook 2010?

I am using Outlook (Microsoft Office Professional Plus 2010) on a Windows 7 Enterprise 64-bit Operating System. Until recently iCloud worked really well - I use it mainly for the calendar functionality. However, following an Outlook crash it has been playing up. I have uninstalled it and re-installed it multiple times with no joy. The issue is this...

iCloud appears to work on the PC and I am signed in. However, the iCloud add-in will not load in Outlook but it does appear there. When I select Options > Add-Ins and then click Go on the COM Add-ins management option, the "iCloud Outlook Add-in" appears unchecked in the list. The location is "C:\Program Files (x86)\Common Files\Apple\Internet Services\APLZOD32.dll" and the load behaviour is "Unloaded". Every time I check the box and hit OK I feel confident it will work, but nothing happens and each time I re-load Outlook and go back into the add-ins window the iCloud add-in is unchecked. 😟

Why is this happening now when it used to work fine?

How do I fix it?

Thanks in advance 🙂