QuickLook permission denied
It's not clear whether this is a recent change in behaviour, or whether you've had this issue for a while. However, QLColorCode hasn't been updated in a long time and my understanding is that it's started to show signs of its age in recent times, with issues such as conflicting with other QuickLook plugins. 

For example, with QLColorCode installed the QLStephen.qlgenerator is not showing text for various text files (instead just showing the typical preview info).

However, some additional things that may be worth trying include:


moving the plugin to a new location, rebooting your MBP, moving the plugin back again, and then rebooting again (or use the qlmanage -r command)
uninstalling the plugin (by dragging it into trash), rebooting, reinstalling it from scratch, rebooting again (or use the qlmanage -r command)
boot your MBP into Safe Mode and then exit by restarting normally
trying the qlmanage -r cache command multiple times


If none of the above suggestions work, then you could try this alternative instead: QLColorCode-extra.

Note: I am not affiliated in any way with QLColorCode-extra.