@tsentalovich, Welcome to HP Support Community.
Thank you for posting your query, I will be glad to help you.
When both the cartridge error light and the wireless light are blinking on your HP DeskJet 3755 All-in-One Printer, it usually indicates a cartridge issue combined with a network/wireless setup problem. Here’s how you can troubleshoot both:
🔧 1. Fix the Cartridge Error
A blinking cartridge light typically means:
- Cartridges are not installed properly.
- Cartridges are empty, clogged, not genuine, or expired.
- There's a problem with the cartridge contacts.
✅ Steps to Fix:
- Power off the printer and unplug it.
- Open the cartridge access door and remove both cartridges.
- Check for protective tape – make sure it’s removed (if new).
- Gently clean the copper contacts on the cartridge and in the printer using a lint-free cloth and a bit of distilled water or isopropyl alcohol.
- Let them dry, then reinsert the cartridges firmly.
- Plug in and turn on the printer again.
🔁 If the issue persists, try replacing the cartridge (especially if it's third-party or refilled).
📶 2. Fix the Wireless Blinking Light
A blinking blue wireless light means the printer is not connected to Wi-Fi.✅ Steps to Reconnect:
- Restore Wi-Fi Setup Mode:
- Press and hold the Wireless and Cancel buttons together for about 5 seconds until the wireless light starts blinking.
- Connect via HP Smart App:
- Download or open the HP Smart app on your phone or PC.
- Add your printer by following the instructions.
- Select your Wi-Fi network and enter the password when prompted.
⚠️ If your wireless router has both 2.4GHz and 5GHz bands, make sure you're connecting the printer to the 2.4GHz network.
🛠️ If the Issue Persists:
- Run the HP Print and Scan Doctor (on Windows) to diagnose and fix issues.
- Try a printer reset by unplugging it for 60 seconds and then turning it back on.
- Update printer firmware using the HP Smart app.
I hope this helps.
Take care and have a good day.
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Max3Aj
HP Support