Hello,
Sounds like that is going to be something on Transflo's end since Logbook is printing it to the PDF just fine. I believe you're the user I was working on this with yesterday and we re-uploaded your signature with a darker image. Hopefully that fixed the problem. If it did not please let us know, either by replying in the forums or go to www.logbook.com and click on the CHAT NOW button on the right side to connect with a technician.
Hope this helps, have a good day.