Before starting to amend the tax return, wait for the tax refund to be received or the taxes due to be paid and processed by the IRS.
See this TurboTax support FAQ for amending a current year tax return - https://ttlc.intuit.com/turbotax-support/en-us/help-article/tax-return/amend-federal-tax-return-curr...
Note - you may have another TurboTax account that was not used to file the 2023 tax return. So the message you received from TurboTax is referencing that account. You can ignore the message since you have filed your 2023 tax return and it has been accepted by the IRS.
