Hey guys, I'm having this same problem. I'm using BTSync v1.1.82 on a QNAP T669 Pro. (x86_64) After reading the solution listed above I still have questions as I do not know how or where to delete the cookies from the host. I'm not well versed in Linux. Can anyone provide a more detailed explanation in doing so? I'd be very grateful as this is a pain in the neck. Strangely, BTSync did work at one point for me as I was able to set it all up. Now, I can't get to the GUI. I just receive the "invalid request" error every time I try to go to BTSync from the Agreement/Acknowledgment screen. Note: I too am running Plex Media Server. The commonality in this thread may point to this as the culprit.
