Most probably the problems appear because you have not parameterized the HTTP requests in your profile. Note that initially all requests are recorded as is. If you use a recorded profile without modifications, WAPT will simply repeat all the same requests with the same values of all parameters. However when working with dynamic site content, some parameters should have unique values for each session.
There is no exact algorithm on how to find all places where the parameterization is required. WAPT can do some automatic parameterization, but only for standard cases. The remaining work depends on your web site, so you have to do it manually. At the same time WAPT provides a convenient interface for this purpose. So, the general approach is as follows.
After recording a profile click the "Verify test" button to verify it. The profile will be executed as is, without any modifications (except for the automatic parameterization made by WAPT). When the verification is finished you can check the "Logs" folder for errors and find the first request that produced an error. The goal is to find dynamic session-specific values inside that request. You can do this by comparing different sessions. Usually such session-specific values are contained inside the request parameters, but they can also be passed inside the main part of the URL. When you find such value you need to find a place (the body of one of the previous responses) from which you can extract it. You can use the “Edit | Find” feature for that.
In WAPT you can select any request and switch to the "Response processing" tab in the right view. Here you can see the recorded request and server response to it. You can use the "Find" option to search for the required values in it. When you find the one you need, you can add a variable by clicking the "Add" button near the list of variables. The goal is to specify how to extract the value from the server response and assign it to that variable. Usually this is done with help of the internal WAPT functions. You can read more about them here:
We also have a demo clip showing a parameterization example. You can download it here:
Part 1: http://www.loadtestingtool.com/quickstart/WAPTdemo-part1.avi
Part 2: http://www.loadtestingtool.com/quickstart/WAPTdemo-part2.avi
After you specify how to extract the value to a variable, you can use that variable with help of the $Var() function.
If you want, we can do all the work for you and deliver the ready to use profiles for your web site. We can do this for additional charge. In this case you will only need to choose load volume parameters and run the test. This will save your time and will demonstrate how the parameterization works on your specific web site, so next time you will be able to do this yourself. Please let me know if you are interested in this service.