This label calls a font that is not downloaded in the stream. If the printer does not already hold it, ZPL falls back silently and the whole layout collapses.
Download the font in the stream, or document it as a printer provisioning step.
^XA^A@N,50,50,R:ARIAL.TTF^FO50,50^FDHELLO^FS^XZ
^A@ naming a font on R: (or E:, B:, A:) with no ~DU / ~DY / ~DT download for it earlier in the stream.
Neither ^PW nor ^LL is set. Both fall back to a value stored in the individual printer, not to a value in the spec — so the same ZPL prints differently on two printers of the same model.
Set ^PW and ^LL explicitly in every format.
This label calls a font that is not downloaded in the stream. If the printer does not already hold it, ZPL falls back silently and the whole layout collapses.
Download the font in the stream, or document it as a printer provisioning step.