Php based site - Login broken - need master coder

Months ago I had a php based website used for tracking my clients and work performed. When I moved the accounts (cpanel based) to my new dedicated server it simply stopped working.. when I say working I mean I can't login. It does nothing when logging in. However, when I use the WRONG credentials it does say the password is wrong... so it is working somewhat to know the wrong password is being used to login. It might be something as simple as not having a service or wrong php version installed on the new server. I just need a resolution to what is wrong.. as I have three of these instances and can't get a hold of the person who made it originally. I am sure someone who knows this stuff will see it easily. If this problem can be fixed - I do want some additional functionality added so the person awarded the project and completes it will get additional work. I need someone advanced as I have had several other coders look at it and couldn't find issue. I will post very good feedback for anyone that can fix this as I know it is difficult and will take someone very knowledgeable.. please no beginners - I am looking for someone advanced to save my application. [login to view URL]