If your earphone work in normal condition then the following are the reasons.
1- your earphone is not stereo based. if you look they don't have three layers of wire.
2- your laptops or computer's sound card does not work or is not installed properly. Note: if you can hear your PC or laptop without the earphone then this is not the case
In general you need to use the earphone that is supported by your pc or laptop. Contact your hardware manager for this.
If you needed further assistance please let me know.