The file in question is stuck with a .PART extension, and I have not been able to rename it through either the client or web site. Since I am an author, and this file happens to be a manuscript, I think you can see the difficulty. Not even copying the file works to correct the issue. The copy also refuses to be renamed.

Transfers are also not working. To my knowledge, my system has no issues that would cause this. What are my options here?

.part files are temporary files created during upload / download.

When you upload a large file, DriveHQ client software (FileManager and Online Backup) uploads the file in chunks. Before the upload completes, DriveHQ server creates a temp file FILENAME.part, which saves the partial file info.

.part files are used for resuming interrupted downloads / uploads. If network connection dropped, or if a user manually stopped the upload / download, the partial file will be kept, allowing the user to resume it later (without restarting the upload / download from the scratch.)

if you see a file with .part extension, it means the file has not been uploaded / downloaded completely. In this case, you need to retry upload / download to finish it. If the file is uploaded by another user, then please contact that user to resume. When it finishes uploading / downloading, the .part file will be automatically renamed to the real file name. 

You should not manually rename a .part file. You can delete a .part file if needed.