Following a system crash, LO will not open any files. Other programs including Firefox and Thunderbird are working normally

Running Windows 10 Pro. LO was 7.1.? and is now Following sudden power failure LO loaded but would not open any files (notably Writer and Calc). I up-dated to current version rebooting several times without any improvement. Where do I go from here? Other programs including Firefox and Thunderbird are working normally.

Click Help > Restart in safe mode > Continue in safe mode and see if you can open files from there.

If still unable to open files, I would hazard a guess that you have anti-ransomware enabled. Add soffice.bin to the list of allowed programs; if already there, remove it and OK then re-add it. See Defender Controlled folder access exception for LibreOffice - The Document Foundation Wiki .

Thank you, EarnestAl, for your efforts but I am still in trouble. First may I add an additional symptom:
None of the LO applications such as Calc and Writer will start from the LO initial window.
My security is provided by Kaspersky Total Security and that does not report anything so it has not intervened. The only Defender that Windows admits to having active is the Firewall. I have not installed any anti-ransomware program. I have done the following with checks of status between each.
Opened in Safe mode.
Updated to
Opened in Safe mode.
Looked for Defender settings
Looked at Kaspersky settings and reports.

Any suggestions?

GNK, Thank you for your suggestions.
I have mostly done a Windows Restart but I believe that at an early stage I did a true Stop and Start but I will do it again.
LO is not started at boot time.
That leaves me to try Uninstall and Install.
Done and sorted.
Many thanks

Kaspersky has anti ransomware included but may be called something else entirely. I don’t know where the settings are located but it is the most likely culprit.

Add soffice.bin to the list of allowed programs/whitelist in Kapersky. If already there, remove it and OK then re-add it.
Note. During the adding procedure, you might need to navigate to C:\Program Files\LibreOffice\program\ and start typing soffice.bin

have you done full power-off&reboot or win10 fakeboot (ie FastBoot / quick restart-thingy) ?
(check power-off buttons are not set to hibernate/sleep ?)
have you tried full uninstall of LO, not just update ? or a PortableLO version to check documents are not corrupt?
is LO set to run as service at system boot ?

have you taken a sledghammer to Cortana? (thats just for fun btw:)