You would have to Print out the online return and compare it to the Desktop return. You entered something different on one of them. Or you haven't updated your program. You can download the .tax2020 file from online for free and open it in the Desktop program. First save your Desktop return with another name to tell them apart.
First download the .tax file from the Online version,
https://ttlc.intuit.com/community/saving/help/how-do-i-save-my-turbotax-online-return-as-a-tax-data-...
Then see, How to Switch to Desktop,
https://ttlc.intuit.com/community/choosing-a-product/help/how-do-i-switch-from-turbotax-online-to-th...
After you get the program installed the first thing to do before you open your tax return is to update the program and install any state programs you had. So you first might need to start a fake return to be able to download the state program (go to FILE - New)
Then you just OPEN the .tax2020 file, go up to File-Open. You don't import or transfer it.
