The value of your target cell is oscillating and Solver can't cope with that.

Doing a manual input MA(x) going from 0 to 10 in steps of 1 change the value in D22 to:

1.123, 1.523, 0.699, 2.290, "#DIV/0!", 2.269, 2.807, 2.712, 2.640, 2.902, 2.464

So if the solver run starts with C2 = 0 and incrementing that Solver will find a maximum for D22 where C2 = 0.6 and the value of D22 is
1.523. Increasing C2 to 0.7, 0.8, 0.9 and 1.0 will not change the D22 value it will still be 1.523

Changing C2 to 1.1 will change the value of D22 to 1.081 so as far as Solver is concerned the maximum value of D22 is 1.523 and this is reached when MA(x) = 0.6

If you add a constraint to Solver i.e. C2 >= 8 then the Solver solution will give a D22 value of 2.902 with a C2 value of 8.6

So inside a range where your target value goes from a minimum to a maximum Solver will work but if you have two or more minimum/maximum values Solver will find a solution based on your starting point i.e. value of C2.


Alf