I received earlier year lump sum amounts on SSA-1099. After entering all requested info TurboTax states earlier year taxable SS ben-TP for my 2018 amount is incorrect?.

That is because your 2018 SSA-1099 box 5 shows the net amount of benefits that you received in 2018.  That box is no longer correct because your lump sum payment changed what you received for 2018.  But the message is just for your records and you do not need to do anything with your 2018 taxes.

Keep a record of it and make sure that you save a note explaining that your actually amount received in 2018 from social security included the benefit.  It means that you were entitles to the amount of the lump sum benefit in 2018, even though you did not receive it until 2020.