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.
- Report the RRSP Contribution on your 2017 (assuming this is a contribution from 2017 or the First 60 days of 2018). When you make the ReFile Adjustment, you must be sure to carryforward, and not use it to adjust your 2017 contributions.
- Wait until your 2017 return is adjusted and a Notice of ReAssessment is issued. You should be able to see in your CRA My Account when it has been processed, and it will say how much you have for "unused contributions".
- Complete your 2018 tax return, claiming the unused contributions.