Have been suffering from error code MS2004 for about a year now. On my iPhone, I believe the code is triggered in Deezer if the track has been linked/searched via an Apple related app such as Shazam. Once linked via an apple app, it seems to be blocked thereafter and not possible to load up on Deezer.
Also finding Deezer not working smoothly when using via Apple CarPlay.
Apple flexing their muscles to push customers towards their own music services.
if using deezer’s own track search facility, the error code doesn’t appear (eg avoid using Shazam to search for tracks, do not use ‘open in Deezer’ button in Shazam /other apps), only use sound search and catalogue searches within the Deezer app ).
Deezer said to me that they are unable to assist to resolve error code MS2004