Connect has a 100Mb upload limit.
I just tried to convert a file that is 97 MB and it failed. Other ideas?
The upload limit has been increased since that post. However if the issue is with your conversion, it is not likely an issue with file size. It could be an object in the PPT that Presenter doesn't know how to handel, to a quiz question that doesn't have an answer. The best option is to reach out to Adobe Support and have them look at the file and identify the problem.
Does Presenter throw any error codes?