iCloud sign in

I have the free version of clean my Mac and the same for Malwarebytes. I was not successful in opening my iCloud on my Mac. It could be that I am doing it incorrectly, but I tried putting a new administrator and it asked for the iCloud sign in and I used the one I already have. It went as far as the passcode and then it failed saying that was incorrect. It was the number they just sent, Then I tried the number they sent yesterday when I changed my password on my iCloud. That didn't work, So I tried a passcode that was given to me for my phone when I bought it. That was it. 3 strikes and you are done. Oh and I plugged my phone into my computer and it automatically backed up to the cloud. I just can't access it on my Mac. Thank you for trying to help me.

Thank You for your response. I did set up another user and that worked perfectly fine but I was still not allowed to use the original user for iCloud. I tried the safe mode and this did not work either. After much research and many different tactics I broke down and called Apple Support. I went up 3 levels and they were still stumped. Info was sent to the Engineers twice and as a last resort was going to have me to some serious in-depth work which I was afraid was over my head. Jessica at Apple was very kind and patient and we tried a few things until at last resetting my Keychain access info was the "Key", no pun intended, to my success. I know have iCloud. Thank you Eric for all your help.