When hop-run defines certain variables before the execution of a pipeline or workflow, for example using system, environment or project variables, they are not applied automatically to a parameter with the same name.
So for example if you set a variable HOSTNAME=localhost in your lifecycle environment configuration file it is defined as a variable.
If you then have a parameter in your pipeline called HOSTNAME then that parameter is not set to the variable.
The effect is that the pipeline thinks the parameter is not set and chooses the default value or nothing if there is no default.
It's quite nasty to figure out why this is not working and counter intuitive.
The better way to do this would be to simply see if there is a variable defined for the parameters and to simply use that.