This is one of those everyone points to the other.  I found that you can check the printer status with an URL like this:

http://localhost:8632/BarTenderWebPrintService/GetPrinterStatus?printerName=BartenderZebra 

The result is:

{"ErrorMessage":"","ExtendedStatusFlags":0,"PrinterName":"BartenderZebra","StatusFlags":0,"StatusText":"Ready","Success":true}

It works great in Chrome.  It used to work in Firefox, but now it doesn't.  I get the following with Inspect: