Have the unused contributions already been reported to CRA? Or have you just added them in TurboTax and are trying to carry them forward? If you could let us know exactly what that error message says and at what point of the return it appears at that would also be helpful.
They have not been reported to the CRA at all. The error appeared after I tried to submit my efile to the CRA, as though they did not accept it. I paid the re-file fee, so the error appears to be one that your error checking didn't catch.
Sorry to hear you are having such a time trying to get that contribution posted. I'm going to suggest you contact CRA (1-800-959-8281) and explain what is happening. They may have that contribution already on file and it might be as simple as importing your information using AutoFill to have the unused contribution imported to your 2018.
If they do not have it on the system, you can do an "adjustment" using your CRA My Account or on paper and mail it in. But your best bet would be calling them first to see how to report it the quickest and be able to use it asap.
You will actually need to take a couple steps here so CRA can recognize that unused RRSP contribution before you can successfully NetFile your 2018 tax return.