You are correct in the fact that you need a resource group for the hours to come through to the corresponding resource planning line. When you write that the system does not accept it, do you mean that the resource field is not editable or do you get any kind of error message? What status is the transaction in?

@Åsa_B thank you for your prompt reply.  I could double click the Resource Group field, system does open for you to enter, but no LOV. then I enter the resource ID, save, but after I save, this field become blank again. and also, nothing is happened on my project resource tab, expected result is, i should see the hours reported. Thank you.

@Åsa_B I just checked the project transaction, there is no price, all 0.

The resource group -is it setup to be used in Projects? (Resource Details/Details).
And is there a cost setup for the reported dates?
 

@Åsa_B Thank you. 

Yes, they are all created as what you described. I have them all screen captured and attatched.

I also added myself employee id into the resource group, and report myself hours, no luck, system refuse to capture the resource group. wondering what setting i am wrong at.

Could you also check if there is a Primary Parent Resource group defined in Resource Details for the Person resource (set on the Connections tab)?. It should pick the primary resource group as default, but it should also be possible to select other resource groups.  I am out of ideas on why your LoV does not show any resource groups.

As has been suggested the default Resource for the Project Time Reporting is picked up from the Primary Parent Resource defined against the employee's resource for the project's company.

When it comes to editing the Resource on the project transaction then this is only possible if the Company Property of EDTRESPT has been set to TRUE - accessible via the Company Details form. Doing this should then allow the Resource ID to be both visible and editable within the Job Details available via the 'Details on Current Row…' context menu.

For the specific issue of a missing LOV and the value disappearing when saving then I am assuming from the earlier screenshot and the highlighted field that the header of Resource Group related to the Work Order lines and that there is no corresponding mapping for this field for the Project lines.

Hopefully a combination of these pieces of information will give you a resolution.
 

@Hugh Batho 

@Åsa_B 

Thank you both. you are awesome.

Glad it worked out