With most streaming services you can set an automatic volume adjustment, which then tries to bring all tracks to about the same loudness. As a result, your tracks will end up sounding different compared to your original master files when heard through these services. Normalization of course changes the dynamics of the audio material.

Unfortunately, all stores have their own guidelines here. Spotify, for example, specifies -14 LUFS as the recommended loudness and also adjusts all tracks to this loudness. Apple Music specifies -16 LUFS, with a tolerance of +/-1 LU. Beatport, for example, has no such guidelines, often the songs here even go to -6/-8 LUFS.

You could test whether this volume adjustment is the difference that ultimately makes your masters sound different. In Spotify (iOS), you can find the option under "Settings > Playback > Activate audio normalization". In the desktop app, it's under "Settings > Audio Quality > Default Volume".

In the end, I would recommend that you observe and adhere to the volume guidelines of the stores. Otherwise you should contact your mastering engineer or the stores directly.