just got your message.
There "shouldn't be" anything more to do.
The USB connection from SSL should be sending keyboard commands.
(acting as a second keyboard)
Does the MAC see the MATRIX over USB? (system prefs & system profiler)
Did you get any popups/setup dialogues when you attached the USB?
Do any of your smaller soft keys on the MATRIX work?
Did you reassign your Transport and Soft Key profiles in the Matrix Remote software from Pro Tools to Cubase user?
If you've done all those and still have problems I'll see if the Manual is available via the SSL site and download it, maybe I can guide you to the right pages?
Cubase Pro 10.5, FL Studio 20, Ableton Live Suite 10.1,Harrison Mixbus 32c, UAD Apollo x series, UR44, UR28m, SSL, Native Instruments Komplete ultimate, NI Maschine Studio, Xfer Records Serum, Lennar Digital Sylenth1, reFx Nexus3, Reveal Sound Spire, FabFilter, Soundtoys, Lexicon PCM, Sonarworks, Slate Digital, Izotope, Brainworx, SPL, Waves, Cableguys, Cytomic, MeldaProductions, AOM, IK Multimedia, DDMF, Boz Digital, Antares Autotune, a bunch of other obscure stuff, TBs of samples, too much hardware to list... PC Windows 10 Pro 64bit, i7-5960x (8 core), Asus x99 Deluxe ii, GeForce 1070 strix, Fractal Design Silent RL2 case, Noctua NH-d15s, 64 GB DDR4 g,Skillz Trident Z 3200 RAM, 1tb Samsung 960 m.2, 3TB segate Ironwolf NAS HDD, 4TB WDRed, 2TB WD Black, Laptop: MSI Ghost pro GS60 6QE i7-6700 Skylake Win 10 64bit, Storage: 32 TB QNAP NAS Raid 50, 12 TB QNAP RAID 1