This message appears when (i) Solver has run for the maximum time (number of seconds) allowed in the Maximum Time box in the Solver Options dialog and (ii) you clicked the Stop button when Solver displayed the Show Trial Solution dialog. You may increase the value in the Maximum Time box (or leave it empty, which means no limit), or click the Continue button instead of the Stop button in the Show Trial Solution dialog. But you should also consider whether re-scaling your model or adding constraints might reduce the total solution time required.