Some time ago I installed Phidgets21 on Mac OS 10.14. Now when I open it , there is login request and I cannot remember the password. How can I reset it or start again. I tried deleting/uninstalling it but asks for the password before performing that task.
As far as I know there should not be a password required to access your Phidgets (unless you mean accessing a PhidgetSBC's configuration page, in which case a factory reset will reset the password).
If you're getting a password prompt when trying to uninstall the Phidget drivers, it's probably your macOS user account rather than anything related to the Phidget.