My HP Deskjet 4100 series is printing blank pages despite having ink. What could be the problem?

This could indicate a clogged printhead. Run the 'Clean Printhead' utility from the HP Toolbox software (accessible through the HP Solution Center). You may need to run it several times. Also, ensure you're using genuine HP ink cartridges and that they are properly installed. Check the ink levels to confirm they aren't falsely reporting as full.