So, as us MIDI guys may know, the CC workaround for getting the looper to work was, at best, finicky. As of 5.0, it doesn't really even work.
Ron over at RJM Music (the guy that makes the Mastermind GT, PT, and LT) has confirmed with one of the Kemper developers that the workarounds no longer work and have been removed (forum link). I've seen some people have some success with this feature on 5.0, but it is dying away. I was personally never able to get the found CC changes to consistently work in the first place, even on 3.x and 4.x.
I understand Kemper is not interested in really using MIDI CC's for much of their base functionality to control every parameter. That's all fine and good. But, with the extensiveness that is their MIDI specification, I see no reason at all why this couldn't be added as a set of SysEx and NPRN commands (and SysEx would be preferred as it is more common and universally supported than NPRN on MIDI devices). Sure, this means people using something like a stock FCB1010 that doesn't send complex MIDI messages would be at a loss, but it seems silly that I have to buy (at $500 shipped) the official remote (that wouldn't work with how I use the Kemper, as with others) just to enable the feature. I already have a full 43" pedalboard - I'm not going to add the remote because its not going to help. The Kemper website says it's an exclusive feature for remote users, which is ridiculous, considering that the remote wasn't announced until after many of us purchased the Kemper itself and found our own solutions for MIDI control.
So, in summation: add SysEx commands and NPRN commands to the MIDI spec to enable the looper on advanced MIDI devices.