Hi,
What happens when you connect it via a USB cable to a working PC? Do you get a red battery light showing that it is charging?
''If it does'' allow it to charge for a while and then see if it can be turned on, or alternatively, leave the USB cable connected and see if it turns on. The light will change to green (only for a minute though) when it is fully charged.
''If it doesn't'', try a different USB cable. If it now shows that it is charging you have a faulty USB cable. If it still doesn't show that it is charging, either the charging circuit or the battery in the speakerphone is faulty.