Hi Ryan,
Please make sure that there is no folder that exceed 15 GB. If there is, please split the folder or delete some content.
If you have Public Folder Mailbox more than 100 mailboxes, please let me know.
Also, make sure that you run your .csv file through PublicFolderToMailboxMapGenerator.ps1 using the command below:
.\PublicFolderToMailboxMapGenerator.ps1 <Maximum mailbox size in bytes> <Folder to size map path> <Folder to mailbox map path>
If you have any other questions or concerns, please feel free to let me know.
Amy