Ok, I had some other issues with formula's not working and was looking at why this was. I discovered in my account info that somehow I have both Office 2016 and Office 365 installed. And the functions that no longer work, are only available in Office 2019 or newer (eg 365). On another laptop that only has Office 365 installed, these functions are indeed still working. And the autocomplete is still working as well.
So the question is; how do I resolve this. I checked the installed apps on the laptop with the issue, but I don't see any Office 2016 apps installed. I see a lot of Office apps though, but I don't want to risk de-installing the wrong apps. Any suggestions how to resolve?
Edit:
Fixed it. I simply installed Office 365 again and now the formula's are working again and the autocomplete is working again as well.