I managed to run pamac again by following the mapac wiki from manjaro.
I did the following:
Dealing with Orphaned Packages
To check to see if there any orphaned packages(packages which are no longer needed) installed you can use:
pamac list -o
To remove all orphans use the command:
pamac remove -o
Cleaning the Cache
When pamac installs packages, it keeps a copy of all the old packages you have downloaded. This cache can be very useful if you have to install older packages in an emergency. However, left unchecked, this cache will grow very large over time.
A safer way to remove old package cache files is to remove all packages except for the latest three package versions using:
pamac clean --keep 3
Finally run
pamac-manager
You should see the add/remove program again
If the steps above do not work for you, disable the flatpak and snap plugins for pamac.
remove the pamac-flatpak-plugin and pamac-snap-plugin
Step 1 : Run “pamac remove pamac-flatpak-plugin pamac-snap-plugin” in terminal
Step 2 : Start pamac-manager
Result: pamac-manager application can start
If you still want the plugins and keep them in disabled state, do the following:
Step 1 : Run “pamac install pamac-flatpak-plugin pamac-snap-plugin” in terminal
Step 2 : Start pamac-manager
Result: pamac-manager application can start
Checks: plugins are disabled