Based on my testing and the comments made here in Splunk Answers related to the add-on, it is no longer supported and no longer works to support pulling down message trace logs. Is there a newer recommended way for pulling down these logs?
We are in the same boat, O365 no longer supports basic authentication for O365 to get those log files.
Having looked at some possible solutions we might write our own TA to get this again working. An alternate solution is to sue a powershell script to dump the log files hourly to a share and import from there.