My mp3 files don′t play

Can you share the website URl?

https://www.zwetasax.com/music/

You are using MP3-jPlayer plugin.
Once check this audio issue to disable all rest of plugins except MP3-jPlayer plugin or use another plugin to verify is audio correct or not.

Please see again. I tried to use the WordPress player. But it still doesn′t work.

Hi,

Disable all plugins and upload the fresh mp3 in media and add the mp3 URL in below mention code in the post/ page. Let us check what is happening.
Audio shortcode:

[audio .mp3]

Here is the tutorial check this https://codex.www.ads-software.com/Audio_Shortcode

I did it, but still doesn′t work. This is the shortcode, which I wrote

[audio mp3="https://www.zwetasax.com/wp-content/uploads/2016/08/in-a-sentimental-mood.mp3"][/audio]

Can you replicate the problem using the default theme with all plugins deactivated? The WP audio player is working fine for me, so this would seem to be site specific.

Also – your shortcode doesn’t look right. Try:

[audio https://www.zwetasax.com/wp-content/uploads/2016/08/in-a-sentimental-mood.mp3]

No closing [/audio] and no quotation marks.

I tried this, but it still doesn′t work

https://www.zwetasax.com/music/

Now is the Thema Twenty Fifteen, I tried with Twenty Sixteen too, and with Twenty Fourteen. Now are also all plugins deactivated.

How did you create a Bulgarian version of WordPress? The lang attribute in the header is set to US English.

I installed the WordPress of Bulgarian, but I changed it in the General Settings of English again.