I use SpaBalancer and still my water smells. What is the cause?

In 99% it is not the water that smells, but the spa rim and the insulation cover. Moisture is "trapped" between them. This moisture is not cleaned and starts to rot. This is what creates the smell. The filters may also not have been cleaned properly or they may have been in use for more than a week. This can also lead to the odor.
Clean the spa rim and insulating cover regularly with a disinfectant. In rare cases, the dosage of SpaBalancer was not sufficient. Increase the dosage in the short term and make sure that the dosage and filter cleaning is done regularly.