Tried all solutions on this site and elsewhere.
The only "work around" is to remember to manually re-enable the icloud add-in every time I open Outlook. Even checked the Registry, but the add-in is set to "3", which should mean "load on open". But it does not; stays loaded for every Outlook session once I enable, but disabled on close every time, hence the need for the enabling "ritual".
And yes, I have tried running as administrator (when it does load on open!) to disable, close, restart and re-enable as administrator, before going back to ordinary user. Re-installed following clean wipe of iCloud for Windows several times.
Some little incompatibility following latest Windows 10 upgrade. I know Apple and MS are not friends, but it worked fie before latest W10 upgrade; there is a simple coding solution in there somewhere.
Very frustrating because my work computer is Windows 190 Pcs but laptop and all mobile devices are Apple, and I really need to keep my calendar synched.