I'm having issues detecting my printer (HP Deskjet 3630), OS Ubuntu 18.04. I've installed HPLIP and when I try to detect the printer via "Network/Ethernet" I get the following answer:
HPLIP cannot detect printers in your network.
This may be due to existing firewall settings blocking the required ports. When you are in a trusted network environment, you may open the ports for network services like mdns and slp in the firewall. For detailed steps follow the link.
http://hplipopensource.com/node/375
I disabled the firewall but that didn't help.
I tried to change "Network discovery method" to mDNS/Bonjour and Avahi and didn't help neither.
Best Answer
Open HP Device Manager > Setup, then choose Network/Ethernet/Wireless network. Then, click Advanced Options.
Choose Manual Discovery and type the IP Address. After that, click Next.
Then, your computer should detect the HP Printer.