Dear applicant,

There`s no need to worry. It is very common to have such issues. Keeping this in mind the examination authorities have made necessary arangements as well. First of all make sure, that evrything in the applying process is done perfectly as asked by the authorities. If everything is done properly, then follow the schedule. If you see that the letter is released and yet you didn`t get it, you need to go to the official website of the examination you are talking about. There will be contact details on the home page itself, either on topmost part or on the bottom. Please contact the authorities. Make sure you have rest of the documents in place and ready to be used whenever necessary. They might ask for a written application as well. State a request and should not be difficult, although try not to delay. 

Hope it helps.

Good luck!