I efiled my Federal return and got an incorrect refund. Turbo tax won't let me efile an amended return. Says I did not efile my return

Are you using desktop software?  If so, maybe TurboTax just needs to know the status of the original efiled return as checked through its built-in tool.

If so, launch TurboTax and open your return.   Then, if it's the Windows version, in the top TurboTax menubar there is a dropdown FILE menu in the top left corner of the TurboTax interface.   Click that FILE heading and in the dropdown choose "Electronic Filing."   Then in the submenu choose  "Check Electronic Filing Status."    Maybe that will "set" TurboTax to know you successfully efiled the original.  If you're using Mac, I don't know the steps, but there's likely a similar way.

TIP:  I don't know if you have already made the changes and amended the return or not, but before amending it's a good idea to make a copy of the original tax data file and an original PDF to backup and archive somewhere safe and secure, in case the amended return gets messed up, or if you ever need the originals for some reason.  Name the files whatever you want as long as you can tell them apart from the amended versions; i.e., something distinguishable such as 2024taxreturn_original.tax2024 as opposed to 2024taxreturn_amended.tax2024 so you don't get them mixed up and save to (overwrite) the wrong file.

What was wrong with your refund?   What do you need to change?  Or did the IRS send you less?   They will mail a letter saying what they changed.   Or were you having the fees deducted from the refund?   There is also an extra $40 or $50 service charge added on.