A password change can require you to verify your account credentials again in your genealogy workflow. If your FamilySearch Login stops working after changing your password, first confirm that the new credentials work when accessing your FamilySearch account independently. Then check whether Family Tree Maker needs the account connection or authorization to be refreshed. Avoid assuming that your family tree itself is damaged simply because login access has stopped. Your FTM data and your account access are separate issues that should be investigated independently. Always keep a recent backup of important genealogy files.