You cannot transfer a 2024 return that was started with desktop software to online software, so, sorry. When you use desktop, the return is only stored on your own hard drive. You cannot get to it from an online account. If you need to switch to online you will be starting over on the 2024 return. You cannot use the license key to pay for online. You will have to pay the current fee for the version of online that you use.
You might be able to get a refund for the download:
To request a refund for a TT product
https://ttlc.intuit.com/turbotax-support/en-us/help-article/intuit-refunds/request-refund-turbotax-product/L834M6uyW_US_en_US?uid=m6meybc2