Sonar 8.5.
Yamaha KX8 controller keyboard (which has Transport Control Buttons)
Akai MPD 226 percussion controller (which also has transport controls)
 
Following some advice I found on this forum, I was able to get the continuous controllers (knobs) on the Yamaha to control  parameters of some Sonar Plug-Ins. So far so good; I hadn't been able to figure that out before.

But I couldn't figure out how to make the transport controls work. Any tips?

Many options:
a) use Generic Surface Controller
b) use ACT MIDI Controller
For both, read corresponding section in the Sonar Reference Guide (2000+ pages, but related section is just several pages). The procedure is not completely intuitive, other documentation/videos about these plug-ins open more questions then provide answers.
c) see the link in my signature. That is "hardcore" way to control sonar from surfaces, with long learning curve and a probability to boil the brain in case you have never programmed before
d) find someone to set it up for you... it takes under 10 minutes (for transport). If you can install Skype+Teamvewer on computer in question, I can do this remotely (PM me here or on my forum if interested).

MMC, but disabled in current version.

CakeHulk
MMC, but disabled in current version.

"MMC" was the name of 32bit Surface plug-in which has translated MMC SysEx MIDI messages into transport command. There was no 64bit version and so it is not in the list.
 
But it is not required to use MMC messages. I must admit that I have not tested that with ACT MIDI/Generic Surface, but that should be definable with both. With AZ Controller I tested that, I even had a preset somewhere... but it really takes 10 minutes to define from scratch, in any from 3 mentioned plug-ins.