We have an issue with Flash player on Firefox where it always picks the lowest bitrate layer, in spite of having enough bandwidth. We see these error in the Flash debug logs , Sat Feb 6 2016 10:44:29 PM.898 [INFO] [org.osmf.net.NetStreamLoadTrait] N

Well, here's the error:

NetStream.Pause.Notify STREAMSWITCH:LEVELMGR: buffer time too low

It's saying that your machine cannot keep a sufficient amount of video buffered at a given bitrate, so it switches to a slower stream.

I'd start by plugging your machine directly into your cable/dsl/whatever modem via ethernet.  If performance improves, do the same thing but plug in directly to your wireless router.  If performance is still good, switch to wireless.  If performance falls apart on Wireless, then you've got some radio interference, which you can try and resolve by changing channels on the router, etc, etc.

If performance falls apart when plugged into the wireless router via ethernet, but it's fine on the cable modem, then rebooting the router, updating the firmware and/or replacing the router (they seem to be fairly short-lived hardware for the most part) might be in order.

If plugging into your cable modem doesn't resolve the issue, you need to have a conversation with your ISP.  Although your connection to your ISP might be fast, the connection from your ISP to the video server might not be, but that's beyond your visibility or control, so you'll have to talk to them.