Anaconda Navigator Does Not Update Packages

I'm trying to update my environment through Anaconda Navigator. But it fails to update some packages. As you can see, the Apply button is inactive and there is a message saying "Package is already installed" but the package is still in Updatable page. Also, Spyder tells me to update nbconvert at each start.

I tried:

• conda update conda
• conda update anaconda-navigator
• conda update navigator-updater
• conda update --all -y

But still these packages are in Updatable list.

This is the conda info output:

C:\Users\user>conda info

     active environment : None
       user config file : C:\Users\user\.condarc
 populated config files : C:\Users\user\.condarc
          conda version : 4.6.8
    conda-build version : 3.17.8
         python version : 3.6.8.final.0
       base environment : C:\Users\ismetb\Anaconda3  (writable)
           channel URLs : 
                          
                          
                          
                          
                          
                          
                          
          package cache : C:\Users\user\Anaconda3\pkgs
                          C:\Users\user\.conda\pkgs
                          C:\Users\user\AppData\Local\conda\conda\pkgs
       envs directories : C:\Users\user\Anaconda3\envs
                          C:\Users\user\.conda\envs
                          C:\Users\user\AppData\Local\conda\conda\envs
               platform : win-64
             user-agent : conda/4.6.8 requests/2.21.0 CPython/3.6.8 Windows/10 Windows/10.0.17134
          administrator : False
             netrc file : None
           offline mode : False

How can I solve this?