Windows 10 shows no connection, everything except MS Outlook 365 works

Hi there,

in my company we have every w10 with latest updates on every pc
since a few weeks users report they cant access ms outlook 365 on their machines and we found out its due to a bug, where the internet tray icon says no connection, but there is, they can access internet and everything except outlook. looks like outlook is dependant on that icon to work.
we tried a fix i found in the internet where I replaced the connecting servers of outlook with old servers, but it didnt work.
odd is, the problem is not every day but completely random. on my own machine i never had that problem.
i tried resolving dns, resetting everything, uninstalling latest updates, chaning adapter settings and what not. without succes. I also tried deactivation of f-secure which is installed by our local it support.

please help

all the best, alex