Adobe Captivate - Close button does not work

I would recommend you DO NOT include the Close button on the playbar as it's asking for trouble because it will only work in certain specific circumstances anyway.

If you are launching your content from an LMS, the Close button is not likely to work unless the content gets launched in its own window.  If the content is playing within a frameset, the Close button will be blocked from working because that could potentially close down the main browser window and shunt the user out of the LMS altogether.

The only real circumstance where the Close button is guaranteed to work is when the content is playing entirely within its own browser window.  It will work for EXE content because that also plays inside its own window.  But when you are dealing with web or mobile delivery the Close button becomes quite unreliable and the end users are NEVER going to understand the technical explanations for why it doesn't work when they click or tap it.  So my advice is leave it out.