Adobe Acrobat Pro DC: unable to validate serial number. [was: NEED HELP URGENTLY]

I recently purchased Adobe Acrobat Pro DC ( Order Number: 12152877759 ) for MAC. I followed the steps to download the program. When I reached to Serial Number page in the installation steps, a yellow massage appear  on the top of the page with : "We are unable to validate the serial number of Adobe Acrobat. Pls contact Customer Service" even before I enter the serial number. When I entered the number sent by the receipt email, the same massage sill on the top of the page without any progress.

I tried many times to uninstall all the related acrobat folders, restart the system & download the program from link Download Pro or Standard versions of Acrobat DC, XI, or X   But Same Problem was Repeated. I also changed my Adobe account & used a new one & still the same problem accrued. I mentioned this problem from yesterday & had been connected with meenakshin83966505 all day long without any solution progress & it end up with this massage (If you still get error message, you need to Contact Customer Care. Sign in with your Adobe ID and then select your product from the list. Then select chat option under "Still need help?Contact us"). From yesterday evening till now I got no reply or connected with anyone to help solving this problem.

I paid 450 US$ to buy this product & can not use it for unknown problem & no support with it !!!!

I need to get a reply how to solve the problem & make the program work. or els I should refund for my payment. Fast action is highly appreciated.

Thanks