Goal Seek and Solver may not have solution

I tried to use Goal Seek and Solver to make sure my Actual data= fitted data by changing the value of k(t), but both Goal seek and Solver cannot provide solution and gives unreasonably smaller value I expecting that the new k(t)(after using Goal Seek/ Solver) will value that not far from the original value of k(t). What kind of iteration that we can use for this kind of problem?
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