I have this Adafruit Mini Thermal printer connected to a Pi running Raspbian Jesse. I have CUPS installed on the Pi and can print directly to the printer without any issues.

But when I try to print to it from a different Linux server, all jobs fail. I have CUPS installed on the Linux server as well and the Pi printer connected over IPP. Printers.conf on the Linux server:

# Printer configuration file for CUPS v1.4.2
# Written by cupsd on 2017-07-05 11:05
<DefaultPrinter ZJ-58>
AuthInfoRequired none
Info ZJ-58
DeviceURI ipp://
State Idle
StateTime 1499227494
Type 6
Accepting Yes
Shared No
JobSheets none none
QuotaPeriod 0
PageLimit 0
KLimit 0
OpPolicy default
ErrorPolicy stop-printer

When I check /var/log/cups/error_log, I see this:

D [05/Jul/2017:11:04:54 +0700] [Job 10] Started backend /usr/lib/cups/backend/ipp (PID 31328)
D [05/Jul/2017:11:04:54 +0700] [Job 10] 1 files to send in job...
D [05/Jul/2017:11:04:54 +0700] [Job 10] STATE: +connecting-to-device
D [05/Jul/2017:11:04:54 +0700] [Job 10] Connecting to
D [05/Jul/2017:11:04:54 +0700] [Job 10] Connecting to printer...
D [05/Jul/2017:11:04:54 +0700] [Job 10] STATE: -connecting-to-device
D [05/Jul/2017:11:04:54 +0700] [Job 10] Connected to printer...
D [05/Jul/2017:11:04:54 +0700] [Job 10] Connected to (IPv4)...
D [05/Jul/2017:11:04:54 +0700] [Job 10] Getting supported attributes...
D [05/Jul/2017:11:04:54 +0700] [Job 10] ATTR: auth-info-required=none
D [05/Jul/2017:11:04:54 +0700] [Job 10] Backend returned status 2 (authentication required)
D [05/Jul/2017:11:04:54 +0700] [Job 10] Job held for authentication.
D [05/Jul/2017:11:04:54 +0700] [Job 10] End of messages
D [05/Jul/2017:11:04:54 +0700] [Job 10] printer-state=3(idle)
D [05/Jul/2017:11:04:54 +0700] [Job 10] printer-state-message="/usr/lib/cups/backend/ipp failed"
D [05/Jul/2017:11:04:54 +0700] [Job 10] printer-state-reasons=none

Looks like authentication (or the failure of) is blocking printouts. I've turned off Authentication on both Pi and the Linux server by changing DefaultAuthType to none in cupsd.conf and restarted the cups daemon on both.

Still nothing prints. Any ideas?

Thank you.

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