Are you downloading your install file from the correct link to work with the volume license?
-and using https://helpx.adobe.com/buying-programs/faq.html (aka Value Incentive Plan VIP)
Also, Mac or Windows and exactly which version of the operating system?
-Recent Mac AND Windows operating systems have been known to cause "odd" problems
-and more help in http://helpx.adobe.com/creative-suite/kb/invalid-serial-number-cs4.html
And finally, Adobe provides almost not support for old programs, but no other user in an open forum can really help with a licensing issue
So you no longer work for the organisation that owns the volume license? I have previously stated, and while I may be wrong, nobody has contradicted me: I don't think you inherit the right to reinstall a volume license as an individual. The license remains with the original licensee and you continue to use it only at their discretion. At least, that seems to be how it is: indeed, organisations who have resold volume licenses have found the whole lot blocked. You would absolutely need the volume install media, and you'll probably need help from the original organisation. Adobe don't support sub-licensees of volume licenes.