ADDMIPSOL and XPRS_CB_SOLNOTIFY

You might want to check the Xpress-Optimizer documentation. The details are described in the XPRSaddcbusersolnotify section:

Status has one of the following values:

0 Solution not checked. Likely because the MIP solve completed before the solution could be processed.

1 Solution is feasible.

2 Solution is feasible after reoptimizing with fixed globals.

3 A local search heuristic was applied and a feasible solution discovered.

4 A local search heuristic was applied but a feasible solution was not found.

5 Solution is infeasible and a local search could not be applied.

6 Solution is partial and a local search could not be applied.

7 Failed to reoptimize the problem with globals fixed to the provided solution. Likely because a time or iteration limit was reached.