I checked in the SMSPXE.log file and it appears the issue was caused by the new computer being unknown by SCCM. It states "device is not in the database.".
From the Configuration Manager console browse to the All Unknown Computers collection from Assets and Compliance\Overview\Devices\All Unknown Computers highlight the Unknown Computer object which is x64 in this instance and use the Add Selected Items button and click Add Selected Items to Existing Device Collection.
From the Select Collection window choose a collection that has Task Sequences advertised/deployed to it and drop the unknown computer into there.
Try the PXE Boot again and it should have resolved the issue.