A couple of suggestions:
1. Make sure you're using Google Chrome as other browsers have limited support.
2. If you're using Cakewalk at the same time as the BandLab mix editor, then Cakewalk could be hogging the audio driver.
Within Preferences->Audio->Playback & Recording, either:
(i) Set your Audio Driver to WASAPI Shared (assuming you're NOT using ASIO) or;
(ii) Check the "Suspend Audio Engine When Cakewalk is not in focus"
Either that or make sure you're not using Cakewalk at the same time as the BandLab Editor.
M.