MacOS
Make sure that LibreOffice has full disk access in System Preferences > Security & Privacy
If still not working see if it it opens in Safe Mode, i.e. without loading your User Profile. If it does then you need to archive your old profile and reset.
Windows
Allow LibreOffice access to Defender controlled folder
The below numbered list is from Use the Windows Defender Security app to allow specific apps
- Open the Windows Security by
selecting the shield icon in the
task bar or searching the start menu
for Defender. - Select the Virus & threat
protection tile (or the shield
icon on the left menu bar) and then
select Ransomware protection. - Under the Controlled folder
access section, select Allow an
app through Controlled folder
access - Select Add an allowed app and
follow the prompts to add apps. You
need to allow access to
soffice.bin
Turn Off Defender Controlled Folder access
Select Start > Settings > Update & Security > Windows Security > Virus & threat protection
.
Under Virus & threat protection settings, select Manage settings.
Under Controlled folder access, select Manage Controlled folder access.
Switch the Controlled folder access setting from On to Off.
3rd Party Anti-virus
If you do have a third party anti-virus go into settings and then look for something like anti-ransomware or folder protection. Have a look at the blocked apps list, if you see soffice.bin in there change it to Allowed (you might have to read AV help if not obvious). Otherwise go to the Allowed Apps setting and allow soffice.bin, this might not be easy so you might have to add the different LibreOffice executables (Calc, Writer, etc.) to the Allowed list click View All files (not just exe) to see it and add it. Note that 3rd party anti-virus might make files Read Only so you can create a new file but you can’t save it subsequently. Sometimes, you might need to reboot after allowing a program access.
If still not working see if it it opens in Safe Mode (Start Menu > LibreOffice > LibreOffice Safe Mode), i.e. without loading your User Profile. If it does then you need to archive your old profile and reset.
Cheers, Al
[edit 2021-05-06 strike out individual executables as it will not help. Thanks to Mike Kaganski]