The model I think makes sense here is the Csikszentmihalyi Flow model, by another name the challenge-skill model of effort: https://en.wikipedia.org/wiki/Flow_(psychology)#Characterist...
Roughly speaking, you might have taken a task that was in the control, flow, or relaxation zone, closer to the center there, and lowered the difficulty so much that now it's flat out in the middle of the boredom zone.
My answer to this is to either seek out much harder problems (moving it back up into challenge, for example), or to change to a task where I have lower skill and so am in the learning mode rather than the execution mode, which I find much more pleasant and compelling than boring.
You change the goalpost, basically, or give yourself a handicap, to bootstrap yourself back up into motivating regions of the graph. Just a model, but I think it's one that is really useful.