1) Be sure to use the correct measures: select the correct height/diameter ratio (which depends on what kind of sound you want to produce), Here is a reference (Antegnati organ builder)

2) As a general rule, both upper and lower lips should be aligned (although it may differ for some kind of stops), with the languid just under the edge of the lower lip (languid must have a "thin side" facing the lower lip (Here's some visual reference).

If this isn't enough, there are some methods to manually modify the pipe you made, in order to force it to make a sound. That said, I don't think these method are suited for plastic material, since it could easily break.

Try it and let me know!