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Printer troubleshooting

Last updated 2026-05-30

Printers are one of the most common "something isn't working" calls — usually fixable in under a minute once you know where to look. This Rundoc walks through the quick checks for receipt printers, label printers, paper jams, and what to do if you're still stuck.

💡 Receipt printer not working? Label printer not printing? Drawer won't pop? All three start in the same place — the ladder in Receipt printer isn't printing below. Walk it in order; the fix is usually in the first two steps.

Rundoo prints through your browser, not through a dedicated Rundoo driver. That means when something goes wrong with a printer, the fix is almost always at the browser or hardware level — check the cable, check the paper, check the system print dialog — not inside Rundoo itself. The one Rundoo-side knob is in the Admin > Communications tab, the General section: Number of thermal receipts printed, which controls how many receipt copies auto-print when a sale completes.

Receipt printer isn't printing

Walk the ladder in order — most of the time the fix is in the first two steps.

  1. Is the printer on? Check the power light. Thermal receipt printers have an LED on the front panel; if it's off, check the power cable at both ends and the outlet. If it's blinking red or orange, that's usually a paper or cover issue — see below.

  2. Is there paper, and is the cover fully closed? Pop the cover, confirm the roll is seated with the thermal side facing the print head (if receipts come out blank, the roll is in backwards — flip it), then click the cover closed until it snaps. A cover that's sitting a millimeter open will flash an error light and refuse to print.

  3. Is the printer connected to the computer? Most Rundoo stations run USB. Unplug the USB cable at the computer end, plug it back in. If you're on network printing, check the printer's status page (usually a small screen on the unit) and confirm it shows an IP address.

  4. Can the computer see the printer? Open your computer's system print settings (Settings > Printers & Scanners on Windows, System Settings > Printers & Scanners on Mac). The receipt printer should be listed and marked ready. If it shows as offline, right-click and remove it, then reconnect it. A Windows "printer spooler" restart clears most stuck-queue cases.

  5. Does Rundoo have permission to print? The first time you print from Rundoo, the browser asks permission. If you clicked Block, prints silently fail. In Chrome, open chrome://settings/content/siteDetails?site=https://app.rundoo.app and set Automatic downloads and pop-ups to Allow.

  6. Try a test print. Open a recent sale in the POS > Transactions > Completed tab, click Print receipt. If that works but new sales don't, the hardware is fine and the issue is elsewhere — set the Number of thermal receipts printed to at least 1 in the Admin > Communications tab (General section) so receipts auto-print at checkout. If neither prints, go back to step 4.

If the printer is printing but the receipts look wrong — cut off at the edge, printed on only half the paper, doubling up — that's a paper-width or driver mismatch. Most receipt printers default to 80mm (3 1/8"); if you recently swapped paper rolls, confirm the width matches.

Label printer issues

Label printers (Zebra, DYMO, Brother) are a bit more finicky than receipt printers because the label stock has to align precisely. Most issues trace to one of three things:

  • Alignment is off. Labels printing half on one sticker, half on the next means the printer has lost track of where each label starts. Run the printer's calibration — on a Zebra, hold the feed button for ~5 seconds until it advances a few labels and beeps; it'll recalibrate automatically. Every label printer's calibration is a slightly different button combo, so check the manual that came with yours.

  • Labels are skewed. If the print is angled or creeping across the roll, the roll isn't loaded straight. Open the printer, pull the stock, and reload it — make sure it's centered in the media guides and the guides are snug but not pinching.

  • Barcodes aren't scanning. Print too light? The print head may be dusty or the darkness setting is too low. Clean the print head with isopropyl alcohol on a cotton swab, then bump the darkness setting in the printer's driver. Print too dark and blurry? Back the darkness off. Barcodes scan best in a middle range — sharp, crisp, not bleeding.

For how to actually trigger label printing from Rundoo, see Product labels.

Paper ran out or jammed

Thermal and label printers both handle this the same way:

  1. Open the cover. There's a release latch on top or on the side.

  2. Remove the old roll. If paper is torn or stuck inside, gently pull it out — don't yank, and don't use anything sharp to dig at it. A stuck scrap can be worked free by rolling it between your fingers; a creased-in-half jam usually needs the cover fully open so you can reach under the print head.

  3. Drop in the new roll with the right side facing up. Thermal paper only prints on one side. Unroll a few inches off the top and set the roll in the bay — the leading edge should come off the bottom of the roll on most receipt printers, the top on most label printers. If the first print comes out blank, the roll is upside down; flip it.

  4. Close the cover until it clicks. A cover that isn't fully latched will flash the error light and refuse to print. You should hear a clear snap.

  5. Press feed once to advance a few inches and confirm alignment before the next customer.

Keep a spare roll near the register. Running out mid-sale is the number-one printer headache, and the fix takes 20 seconds if the spare is right there.

Supported printers

Rundoo works with any printer your computer can see through the browser's print dialog — that's the design, and it's what makes swapping hardware easy. That said, the setups our customers run most are:

  • Receipt printers: Star TSP100 / TSP143 series, Epson TM-T20 / TM-T88 series. Both connect via USB and work cleanly on Windows and Mac.

  • Label printers: Zebra ZD410 / ZD420 (most common in stores doing shelf labels and product tags), Brother QL-series for lighter duty.

If you're setting up a new station and not sure what to buy, call Rundoo Support — we'll point you at what your vertical typically runs.

Still stuck?

If you've walked the ladder and the printer still isn't cooperating, it's time to call Rundoo Support. (650) 334-3205 reaches a human who can screen-share into your station and debug with you in real time. When you call, have the printer's make and model handy, and mention what you've already tried — saves us both a few minutes.