Seems like any change on your system caused. You either need to reinstall the software, so the installer will write the license information again on the boot sectors of your HDD.
Searching the internet for repair strategies for CS6 are not successful. For older suites, Adobe had a repair tool.
Last year my pc had a number of crashes due to a problem with the SSD, so I installed the software already a couple of times and run out of possibilities to reinstall.
Thanks already, maybe a system recovery can do the trick, if not, I will be back
I tried a system recovery yesterday, which diid not help at all. Re-installing the program is not really possible because of the fact that my system crashed 3 or 4 times last year. Last year I could get some help by phone but now I discovered that that helpline is no longer available.
Ok, but there still is a helpline. Try that one.
Apart from that, why would reinstallation not be possible. It wipes the license data, so you do the license procedure again.
A system recovery does not work here, that's why it wasn't suggested.