Why do I see "ERROR: 5 - ?422 Error: Solution is not available" when the optimizer found a feasible solution?

Looking at your log, it seems like you first solved the problem, which did indeed produce a feasible solution, then used "fixglobals" to fix all the integers to their current values and solved the resulting LP, and the latter went infeasible? This can unfortunately sometimes happen when the first solve finds a solution that is within tolerances but still has some slight infeasibilities which can lead to presolve declaring the problem infeasible after fixing those values.

You could try to experiment with bit 10 of REFINEOPS (https://www.fico.com/fico-xpress-optimization/docs/latest/solver/optimizer/HTML/REFINEOPS.html) which has been introduced specifically for this scenario and which will try to ensure that we will only accept solutions during the first solve that would stay feasible after fixing and represolving, but note that this can increase solvetimes, both due to the effort of checking this, and even more so if we actually have to reject solutions for this reason.