OK! Go to your ACARS module located in core/module/ACARS folder, open acars.php with notepad or notepad++. Now there is a section called function viewmap() make sure, acars.tpl is rendered there.
Then check where the acarsmap.tpl located in your skin folder, it's supposed to be in the main folder of the skin, if it's in some other folders, take it out and put it in the main folder. Also, put back your custom made skin, so that we can see the result. I think in your skin the acarsmap.tpl is not being read somehow!