We have not seen this problem yet in our lab, please, could you provide more information regarding type of machine, OS version, printer involved, ZPL code, type of environment, Solution architecture, etc.
Please, could you report the issue to our Zebra Technologies tech support to process your request as well.
I'm having this issue on Safari (12.0.3) but I can run the sample perfectly in Chrome or Firefox on the same computer with the same BrowserPrint service running in the background so it's really a browser specific issue. We are using BrowserPrint in our web application to allow users to print labels directly from our web application and it was another user who reported the issue with Safari to me. And i'm having the exact issue when I try it in Safari...
Looks like the call is being blocked because the sample is being hosted on a SSL connection and the BrowserPrint.js tries to call http://127.0.0.1/default?printer on a HTTP connection which causes Safari to block this request because it's unsafe.
OS: macOS Mojave
Printer involved: GK420d
ZPL code: none, BrowserPrint.getLocalDevices can't even fetch the printers because all calls are blocked
Browser: Safari 12.0.3
BrowserPrint version: v126.96.36.1999
BrowserPrint js version: 188.8.131.52
Thank you for the feedback, I passed the information to our dev team, however, in order to escalate the issue we need that you report it to our Zebra Technologies tech support .(please, use the link and open a case)