This is a draft and any contribution is welcome. Feel free to add, change or comment anything. It'll remain under my user area until it's useful.
Generic troubleshooting
Sometimes a basic feature of Vim does not work as expected, the following instructions can help to find out where the problem is located.
Discard Vim executable
Run vim -N -u NONE and see if the problem persists.
- The problem persists. That means the problem could be on the Vim executable. Verify enabled features.
- The problem went away. It is time to discard the vimrc.
Verify enabled features
Check the feature you need was enabled when Vim was built. Use the :version command to see if said feature is enabled.
- Some/any needed features are disabled. Build Vim with desired feature enabled or use your package manager to install it.
- All needed features are enabled. What to do here?
Discard vimrc
Run vim -N --noplugin and see if the problem persists.
- The problem persists. The reason of your pain is your vimrc.
- The problem went away. The next step is to discard the plugins.
Discard plugins
Run vim -N -u NORC and see if the problem persists.
- The problem persists. It looks like the issue is related to a plugin.
- The problem went away. Maybe the problem is that Vim is running in compatible mode, verify that with :verbose set cp? to also see where it's being set.