I solved the problem myself through a work around.
I still can't understand why the Ccleaner Professional installer can't work on my PC.
I tried to launch it from another Windows 10 1909 PC and I could see that in that case the installer worked smoothly.
The work around consisted of uncompiting the .exe file via 7zip.
In this way I was able to generate the various installation files of Ccleaner Professional, Speccy, Recuva and Defraggler.
These executables were found to be launchable without problems.
The rest will remain a mystery, as will the fact that they have not received any response from the technical support. I expected to receive them in this forum. Too bad.