Have you tried sending those messages via email instead of using Nabble?
If your message gets through the list (and get archived at Nabble), then we will have to investigate what is wrong with your Nabble account. So, first, please make a test (by sending an email to the mailing list) and let us know what happened.
You should send an email to the mailing list address (e.g., grass-stats@lists.osgeo.org) and that's it. The subject will be the "topic" and the message will have your explanation and questions. You may use rich text formatting for code, but this is not required.
Nabble won't send those pending posts to the mailing list again. If those posts still make sense to you, you can post them again and delete the old ones. This should work now because you were able to send an email to the mailing list and it successfully got through.