Sounds like you might have bought the Desktop program download. You can not do 2018 online anymore. Online is closed to get ready for 2019.
You need to download the 2018 program and install it on your computer. How to download your program…..
https://ttlc.intuit.com/community/installing/help/how-do-i-download-the-software-i-purchased-at-turb...
