I bought Vegas movie studio from the website itself and was emailed the serial code to register it and everything... however, on the website itself it says its a valid serial number but when I download it and try getting on the Vegas check and tuning, it says in invalid. What do I do?
Do you mean the "MAGIX PC Check & Tuning" software, which is included in the "download manager"? It may just be a teaser to trial the application and probably needs to be purchased separately. Please see here https://www.magix.com/us/supplementary-programs/pc-check-tuning/.
Can you post a screenshot from the website itself where it says it's a valid serial number for other software than your Movie Studio version?
Please note also that "If you have any questions about an Online Shop order, please contact VEGAS support"..