Hi Christopher,

It's expected that very large MPP file will take some time to upload and process - but a timeout shoudln't happen in theory. I assume that the timeout you're experiencing here happens at the Web Server level. If the web server decides to cut HTTP request if it takes too long, there's nothing that PPM server can do.

Can you double check your Web Server configuration and see how to increase the request timeout limit? FYI I think that this upload operation is a HTTP POST operation.

I ended up getting it to work by switching the project to MSP plugin, downloaded the existing WP, switched it back to MSP upload, and was then able to upload with no error. I think switching the project control reset the WP somehow. 

Switching between MSP Sync mode doesn't reset anything - a most likely explanation is that you uploaded your MPP file at a time where the load on the server was lighter, and the sync completed fast enough to not trigger your web server's timeout.

Or maybe there was something in your original MPP file that was causing some long processing, and the file downloaded with the plugin didn't had it as the file is generated from scratch by the plugin.

In any case, glad that this is sorted, but you may still want to check your web server timeout configuration if this issue occurs again in the future.