in order to open vault you have to advance Amy/Emma first Amy can be advanced in veronica path or if you are having trouble or getting bugged then open your save file with notepad then ctrl+f search for the_vault 2nd line change the value to 1 if its 0 it must look like thisWell I am sorry and relieved to hear that. Sorry that your in the same boat and relieved that I'm not the only one.
<Name>discovered_the_vault</Name>
<Value>1</Value>