The icons on the Button Bar display the actions that will take place when they are clicked (rather than reflecting the current status).
The Audio icon with the cross signifies that the audio will stop when clicked.
The corresponding rollover tooltip text is in line with this, too.
When you hover over the Audio icon with the cross, the tooltip text reads "Pause Audio".

The AutoPlay icon works the same way (i.e. click to do what the icon signifies).
A traditional triangular 'play' icon is displayed when AutoPlay is off (the user clicks the 'play' icon to start AutoPlay) and a 'pause' icon is displayed when AutoPlay is active (the user clicks on the 'pause' icon to stop AutoPlay).

If you want to reverse the way the Audio icons work, then open the gallery's 'jbcore/classic/theme.css' file in a plain text editor and change lines 855 to 861 (inclusive) from:

.jb-bb-button.jb-bb-btn-audio:before {
    content: "\e00c";
}
.jb-bb-button.jb-bb-btn-audio.jb-status-playing:before
{
    content: "\e00d";
}

... to:

.jb-bb-button.jb-bb-btn-audio:before {
    content: "\e00d";
}
.jb-bb-button.jb-bb-btn-audio.jb-status-playing:before
{
    content: "\e00c";
}

If you want to change the rollover tooltip text in your gallery, then you can do so via the languageList configuration option.
This option is not available in the JuiceboxBuilder-Pro interface and must be added to your gallery's configuration options manually.
Please see the International Gallery Text support section for details. (The languageList configuration option was originally intended to be used for translating rollover tooltip text but can just as easily be used to modify the default text.)
Information on how to manually set configuration options (either in the 'config.xml' file or in the embedding code) can be found here.

I hope this helps.
Please let me know how you get on and if I can be of any further assistance.
Thank you.