How to clean a stain mirror?

I got a furniture 8 months ago but the issue is the mirror it has a stain or huge line inside the mirror I tried clean it but nothing is helping like I use a newspaper, tissue, cotton cloth to clean it glass cleaner and even a rubbing alcohol too but the stain/ line does not go what can I do to clean the mirror. ... show more I got a furniture 8 months ago but the issue is the mirror it has a stain or huge line inside the mirror I tried clean it but nothing is helping like I use a newspaper, tissue, cotton cloth to clean it glass cleaner and even a rubbing alcohol too but the stain/ line does not go what can I do to clean the mirror. Now I'm totally helpless :(
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