how to create a Purchase order for a BPA with service line type?

Summary:

Hi everyone. I usually work with blanket purchase agreements and easily Creating an Order gets linked to the BPA but right now I am experiencing a hard time trying to do it with a BPA with Services line type. I just can't create an order adding the same supplier and item description, exacly as I have it in the BPA

and when I try to add the BPA in the corresponding field "Source Agreement" it just doesn't load the BPA from the supplier with that same item description as a service line type

Why this happens if I can do it with goods line type why I can't do it with service line type??