Yeah a lot of site block manipulation of audio, that's why

Can you elaborate what's the issue you are seeing at namastesumalya@gmail.com

It works, depends on which website you are using. Some website block web audio api and my extension even every volume manipulation extension only able to manipulate web audio. If the website works on different audio style then this extension may not works. Also Yeah this is only accessible via browser shortcut or extension manager, can you suggest what do you want me to do?