In trying to do a restore I find I have several points to choose from and I've tried several. It goes through its cycle and ends up with the message 'cannot restore'. I don't have any viruses or malware that I can find, I keep it as clean as possible. At the moment I'm not having any major problem requiring a restore, but I have in the past and want it available if I need it in the future. I'd appreciate any help.

Just a guess but maybe something got corrupted.

Right click My Computer > Properties > System Restore > Turn off system restore on all drives.

This will purge all the old restore points and clean out your System Volume Information folder(s).

Turn it back on.

See if it's fixed by doing a restore.