I purchased standard turbo tax and found out afterwards that I can’t use it on my computer. Can I use turbo tax online with what I already purchased?

No. The codes for TurboTax CD/Download will not work with TurboTax Online & vice-versa.  You can get a refund for the product you don't want by using the form on this page: https://turbotax.community.intuit.ca/community/after-you-file-questions/help/how-do-i-get-a-refund-for-a-turbotax-product/00/873559