SergeiBaklan
Thank you for your reply.
The compute I work on initially had a Microsoft Office Professional Plus 2016 (by the way, I had discovered that the release was installed with a pirate licence that the IT service provider - now sacked - had sold to me as authentic).
The firm I work for, opted to purchase few licences of Office 365. I installed one of the licences and everything worked well for a while.
Last week, after writing on this forum, I checked and for some reason it appeared that the version installed is MSOffice Professional Plus 2016.
I tried to switch licence, but I did not work. I tried something more drastic: I uninstalled everything (MSOffice and all other software related to that: Skype, Skype for Business, OneDrive, all spellcheck plug-ins everything that I could recognise related to MSOffice) and downloaded and installed Office 365 from the website over the weekend using the licence .
The process went through well and I got the message of a successful installation. Nevertheless, when checking, there you go, the zombie MSOffice Professional Plus 2016 is there again.
Whilst this explain why IFS does not function, reveals another problem: I can't switch to another licence and I am not able to totally remove the MSOffice Professional 2016.
I am tempted to reinitialise the entire pc, but maybe you can suggest a more focused, less drastic solution to kill the zombie once for all.
thank you,
Damiano