I expect that you have either 2 Tablix's in the report OR you have the hidden property set on the column of the single Tablix that has your data that is hiding it based on the value of the parameter.
If you have 2 Tablix's, you will need to add the column to each tablix.
If you have hidden properties set on the column, you will need to adjust the visibility to work differently.
The above is all just my opinion on what you should do.
As with all advice you find on a random internet forum - you shouldn't blindly follow it. Always test on a test server to see if there is negative side effects before making changes to live!
I recommend you NEVER run "random code" you found online on any system you care about UNLESS you understand and can verify the code OR you don't care if the code trashes your system.