The problems with SCCP Manager are manifest and not really compatible with the Data Model for FreePBX 12 and above. There are issues with it that make is not really appropriate for systems that have an "outward facing" interface.
I've been busy with other projects, so I haven't had time to rewrite the module to conform to the new coding and visual standards for FreePBX 13.
One thing you can check is that you actually have softkeysets defined in your database. As noted in the docs, there is a default softkeyset called (not surprisingly) "softkeyset". If you want to add additional keysets, you can.
Yes, actually, I do. The installation process still has issues - I wrote the system to manage an existing and working SCCP installation, so a lot of the "seeding" of the data is a little off-kilter. I actually have it installed on one of my FreePBX 13 installations. Unfortunately, because of the new BMO interface, the system doesn't meet the safety standards for FreePBX anymore. The system, instead of using BMO, does direct calls to the database (which was normal in FreePBX installs at and before 1.8). This method is no longer optimal and shouldn't be used.