If you open an old Patran model which was created before MSC Sinda for Patran installed in your computer, you will not see MSC Sinda in the solver list. That is because the old model was based on the old template.db which does not include MSC Sinda preference at all. To add MSC Sinda preference into the old database, please open the old database first, type load_sindag() in the command line (usually at the bottom of the Patran GUI), click Enter to run this function. This will add MSC Sinda preference into the old database and make MSC Sinda as the default solver. If you want to keep Nastran as the default solver, please run load_sindag_sindag_nastran() instead. You can always change the solver by Preferences/Analysis/Analysis code no matter which function is used.