I’m the administrator of the site: my console is open but there are some users that are not able to write in the chat.

Please, check if you have reached the maximum number of opened conversations allowed as set in the plugin settings.

My browser crashed, have I lost the conversation with my customer?

No, the conversation ends only if one of the two speakers ends it on purpose clicking on the “End Chat” button.

Chat popup is not available. Why?

To show the chat pop-up correctly, the theme installed on your site needs to use the function wp_footer()” in its templates.