Conda install and update do not work also solving environment get errors

I am using anaconda as below:

(base) C:\Users\xxx>conda info

     active environment : base
    active env location : C:\Users\xxx\Documents\ANACONDA
            shell level : 1
       user config file : C:\Users\xxx\.condarc
 populated config files : C:\Users\xxx\.condarc
          conda version : 4.7.11
    conda-build version : 3.18.9
         python version : 3.6.9.final.0
       virtual packages :
       base environment : C:\Users\xxx\Documents\ANACONDA  (writable)
           channel URLs : https://repo.anaconda.com/pkgs/main/win-64
                          https://repo.anaconda.com/pkgs/main/noarch
                          https://repo.anaconda.com/pkgs/free/win-64
                          https://repo.anaconda.com/pkgs/free/noarch
                          https://repo.anaconda.com/pkgs/r/win-64
                          https://repo.anaconda.com/pkgs/r/noarch
                          https://repo.anaconda.com/pkgs/msys2/win-64
                          https://repo.anaconda.com/pkgs/msys2/noarch
          package cache : C:\Users\xxx\Documents\ANACONDA\pkgs
                          C:\Users\xxx\.conda\pkgs
                          C:\Users\xxx\AppData\Local\conda\conda\pkgs
       envs directories : C:\Users\xxx\Documents\ANACONDA\envs
                          C:\Users\xxx\.conda\envs
                          C:\Users\xxx\AppData\Local\conda\conda\envs
               platform : win-64
             user-agent : conda/4.7.11 requests/2.22.0 CPython/3.6.9 Windows/10 Windows/10.0.16299
          administrator : False
             netrc file : None
           offline mode : False

Now I have 2 issues that stop my work.
1) I cannot use conda install for any package.
It will give me the error in solving environment list this:

failed with initial frozen solve. Retrying with flexible solve.

then it will fail again and give message like this:

Found conflicts! Looking for incompatible packages.
This can take several minutes.  Press CTRL-C to abort.

Even after the checking for incompatible packages, it didn’t give me the solution.

2) When I want to upgrade or downgrade conda by the command:

conda update -n base conda

or

conda install conda = 4.6.11

It will give me errors again in the solving environment, and I think this is related to the first issue.

Now I cannot use conda for anything, please advise and thank you!