When you use the function Get Std. Service Codes, these will not be linked to a service item.
In the process you want recurring service codes to be linked to each service item you choose.

- create the service order
- fill the service lines with the service items that need service
- choose a Std. Service Code for each serviceitem
- then complete the servicelines or service item worksheet

Now after selecting a service code, you manually need to link the lines to a serviceitem using the Service Lines page.