Hello JohnAtkins,.
If you have not already resolved this issue, we suggest you search our online knowledgebase for this product: VersaLink C400.
Alternatively, you can visit our Contact Us page for other support options.
We have serval new Versalink C400s connected by USB to Macbooks running Seirra 10.12.6, most of the time take 15-30 minutes before the job it will print. With the same model printing from a Windows PC works just fine. We have updated the print drivers on the Macs and ugraded the firmware to the lastest on the printer.