Unable to get IP address via DHCP on HP ProLiant DL380 Gen9 with Debian

I'm having trouble getting an IP address via DHCP on my HP ProLiant DL380 Gen9 server running Debian. I've tried various troubleshooting steps, but nothing seems to work.

Error messages:

• "No DHCPOFFERS received"
• "No working leases in persistent database - sleeping"
• "Activation of network connection failed" (GNOME)
• "IP configuration unavailable" (Plasma)

Hardware:

• HP ProLiant DL380 Gen9 server

Software:

• Debian operating system
• GNOME and Plasma desktop environments

Troubleshooting steps:

• Checked network cable and ensured it's properly connected
• Restarted network service
• Set /etc/NetworkManager/NetworkManager.conf managed=true

Additional information:

• Internet worked during the Debian installation process, but not after booting into the installed system.
• The problem occurs on both GNOME and Plasma desktop environments, but Plasma provides a slightly more helpful error message.

I'd appreciate any help or guidance on resolving this issue. Has anyone else experienced similar problems with DHCP on a HP ProLiant DL380 Gen9 server with Debian?