“Parameter is not Valid” is an error you get while attempting to print your NYSC call-up letters for Batch A 2016 orientation programme. i also experienced this too and it took a while for the issue to reolve on its own. A lot of people have called and sent messages to ask what could be the cause of that. I have gone to several online forums and social media platforms where many have attracted this error to network issues. I seriously doubt that since prospective corps members could log in to the NYSC portal and do other things than print call-up letters. What Could Be The Cause of “Parameter is not Valid” Error? The only plausible explanation for getting the “Parameter is not Valid” while trying to print your NYSC call up letter on NYSC website is that it has not been uploaded. We informed you in this post that printing of call-up letters will take place between Wednesday, 20th and Wednesday, 27th April, 2016. I believe that the call-up letters are being uploaded in batches and those getting the error are those whose letters have not been uploaded. You can check the NYSC portal back later. This post is meant to just put your mind at ease that you are not the only one getting this error. There are so many people out there experiencing this too. UPDATE: Some of those that got the error messages have now seen their letter. Just keep checking.