Please try to understand the working of VF06. VF06 is not producing any invoice itself or you can say differently from VF04 or VF01.
Instead VF06 is create a background job only, for producing invoices. you can chcek that job in tcode SM37. Then the background job runs separately using the same standard code used by VF04 tcode, to produce invoices.
So you can check any log at background job level not at VF06 level.
Goto T.Code VF06.
Enter the Sales organisation and Distribution channel and division.
Enter the customer number if you want to create billing document for a particular customers.
If you want for range of sales documents you want to create billing then enter the range in sales document.
Documents to be selected are sales orders if you want to create billing with reference to sales orders or tick deliveries if you want to create with referencce to delivery.If you want with reference to both then tick both.
Select start immediately.Donot Tick Test.
And in the output tick "list display" and "issue collective processing log".
A job number will be appeared here.
Note down it.
If you want current status then goto SM37 T.Code and then release it if the status is not released.
After that check in V.21.
It is the standard process.
If you took the print then it will come in the SP01.