What version of OR-Tools and what language are you using?
Version: v9.6
Language: Python 3.8

Which solver are you using (e.g. CP-SAT, Routing Solver, GLOP, BOP, Gurobi)

CP-SAT

What operating system (Linux, Windows, ...) and version?

Linux Ubuntu 20.20

What did you do?

Added pseudo_costs in ignored_subsolvers list:

solver.parameters.ignore_subsolvers.append('pseudo_costs')

What did you expect to see

What did you see instead?

An error message is returned:

"Invalid parameters: subsolver 'pseudo_costs' is not valid"

Make sure you include information that can help us debug (full error message, model Proto).

The below will work in 9.5v but not in 9.6v

from ortools.sat.python import cp_model

model = cp_model.CpModel()

x = model.NewIntVar(0, 10, 'x')
model.Add(x <= 9)
model.Maximize(x)

solver = cp_model.CpSolver()
solver.parameters.log_search_progress = True
solver.parameters.ignore_subsolvers.append('pseudo_costs')

solver.Solve(model)

Anything else we should know about your project / environment