Make It Work With Outsource Testing
I think that for a newly installed software to work, it has to be tested by an outsider. It should be Outsource Testing. People who will do the testing will be as objective as possible because they do not know anybody in the company who might be affected with the results of the testing and since they are hired to test the software, they only have to test it. Unlike personnel in the company, cannot be separated from their daily tasks. So testing will be interrupted all the time. Thus testing will not be completed. Even if it would mean additional costs for the company, in the long run, it will all be worth it.