TS4124 iTunes Match is terrible
For some reason Apple chose to refuse iTunes Match's support for songs with bitrate lower than 96kbps. (check http://support.apple.com/kb/ts4124)
Why this stupid decision? It has been some time since I discovered the "just works" slogan by Jobs isn't worth **** anymore, just like Google's "don't do evil".
I just paid USD25 for this service and I'm feeling extremely frustrated.
Don't tell me to "just rightclick and convert to AAC" because when you reconvert a file you lose quality, create duplicates, etc, etc.
You can try selecting the files and choose "Create AAC version" from the context menu of iTunes. This usually works as it create a higher bitrate file. Still, it is not foolproof, sometimes, it may create bitrate of 80kbps or higher. iTunes match requires at least 128kbps for matching. You just have to trial and error. A third-party audio converter might also help to force convert everything to 128kbps.