Sales order is picked...

Sales order is picked and shipped but the status is Ineterface to receviable
I cant find the AR invoice  against it
The invoice data are not in interface either

What could be the reason

what do you mean by

what do you mean by 'The invoice data are not in interface'??

 are you suggesting that the SO details are not in RA_INTERFACE_LINES
_ALL
If yes, then check again in RA_CUSTOMER_TRX_ALL

If the data is not present in any of the table then invoice is not populatedin interface tables..so there might be some issue from where the data is coming..

Lets us know a bit more

status is interfaced means ..

status is interfaced means .. data may be in the ra_interface_lines_all..

Try running workflow background process program. This will pick up these values and creates invoice

well I dont think the above

well I dont think the above comments are true..
The status of the SO would remain Picked if we don't run WF Background after shipping the SO line

As the line status has changed to interfaced to receivable and still the data are not in interface, there can be two reasons
1. WF is erred out in customized acitvity.
2. If its an ISO then the create AR invoice program has failed

Invoice creation issue

I think if you run the Workflow background process it will interface SO info only to AR Invoice interface tables and won't create an Invoice.If your SO info is present in AR Invoice interface table try submitting Auto Invoice import program with your SO number as parameter.Once the program completes successfully AR Invoice would have been generated.

Let me know if this helps.

Regards
Rajesh 

Try to run workflow

Try to run workflow background process concurrent program.