Trouble Finding More than One Feasible Solution
For some models, ILOG CPLEX finds an integer feasible solution early in the process and then does not find a better one for quite a while. One possibility, of course, is that the first feasible solution is optimal. In that case, there are no better solutions.
One possible approach to finding more feasible solutions is to increase the frequency of the node heuristic, by setting the HeurFreq parameter to a value like 10 or 5 or even 1. This heuristic can be expensive, so exercise caution when setting this parameter to values less than 10.
Another approach to finding more feasible solutions is to try a node selection strategy alternative. Setting the NodeSel parameter to 2 invokes a best-estimate search, which sometimes does a better job of locating good quality feasible solutions than the default node selection strategy.
