Hi Christiaan,
Thanks for your updates.
Since you have uninstalled Office, you can reinstall Office and check if the issue disappears. If not, you can refer to the suggestions I mentioned in my first reply and check if it helps.
If they don't help, I suggest you change another network environment, temporarily turn off proxy, firewall and antivirus programs on your computer and
try installing Office from Office 365 portal again.
Here is an article for your reference:
Troubleshoot installing Office 365, Office 2016, and Office 2013
Regards,
Tina