Website error with Paypal

I have a classified advert website which uses php/mysql and Paypal as payment processor. This has been working fine for over a year but in the past few weeks, payments have not been working correctly. This is the problem: A new customer signs up on the account register page, they are then transfered to the packages page, they select a package and are then transfered to paypal to make payment. When they are transfered back from paypal they are ment to have the package (which is a number of classified adverts) credited to their newly created account on the website BUT instrad, then they are transfered back to the website their account is not credited and shows and "inactive" account page. Expected result: I expect you to be able to troubleshoot this problem and fix it, so when a user selects a packge and is transfered back from paypal their account is activated and package (number of classifed adverts) is credited to their newly created account. Timeframe: I require this completed within the next 2 days. Money: This is on a tight budget as i am not being paid from the client so budget must be low. I have had a few users try this before after paying them for it so payment will be made 100% after you fix the issue. No escrow for this. Check my feedback as i always pay when you do a good job. If work is good then i am likely to use you again as i have a large amount of php/mysql projects.