If the custom workflow is working when used locally then at the server something is missing in the configuration for the custom workflow.
I suppose the development project and the live site both use Sitefintiy license for the same edition, professional and enterprise edition
is needed to use custom workflows in sitefinity and the custom workflow is build as class library project composed of a class for the modified workflow activity that sets author to news items and the workflow.xamlx.
Double check if the custom workflow coming from the class library is part of the bin folder for the project deployed live and is the workflow registered.
Register the workflow virtual path as described in the documentation
and restart the application after the registration of the virtual path so it will become active.
Possibley the restart is still needed to start using the new virtual path.
When placing the dll library for the custom workflow in the bin folder build sitefinty project if sitefintiy is deployed as asp.net web application. If it is used as asp.net website no recompilation is needed when adding new components to the website.
To avoid building sitefintiy when used as web application build the project locally and move custom workflow dll and sitefintiywebapp.dll to the live site.
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