Restart MixPad and reload your project; reset track effects via the track menu.
In Windows Sound settings (right-click speaker icon > Open Sound settings > your output device > Additional device properties > Levels > Balance), ensure left/right sliders move independently—update audio drivers if not.
Check MixPad's master output for mono mode (toggle off) and test with headphones vs. speakers; reinstall MixPad if persistent.
If no joy, install the latest release.
For one-time licensed users upgrades are free for up to six months from purchase date. After that, MP will continue to fully function but a fee is required in order to register the newest. Retain your old install file and registration info. If there's an issue, you can always revert.