Restoration points fail to restore

I'm trying to restore my system to an earlier state (to avoid a malfunction for which nobody in these fórums offered an answer).
I see several restoration points more than one month old (which is about when I began to notice the malfunction), but none of them actually works.
The operation seems to unravel normally through its usual steps, but when it is over and the laptop restarts anew, it shows a notice saying that the restoration did not take place and that no changes have been made; no other explanation. And the same thing for all those restoration points.

Thanks in advance for any help
ACA

Try performing the system restore from safe mode. Make sure to boot back into safe mode after the restore, then boot again into normal mode.

Do you have Bit Defender as an antivirus program?

Tnanks, pbcopter; I'll follow your tip.
As for the antivirus program, no, I haven't got Bit Defender; I have Panda, a Spanish one which I pay for and that I've had for many years; quite reliable, I think.
ACA

The reason I ask, is that Bit Defender interferes with System Restore and in order to perform one, it must be done in safe mode. This may be true with other anti-virus programs as well.

True; that seems to be the issue.
Thanks a lot, pbcopter.
ACA