Diagnosis
A steady orange light on the Internet (globe) port means the router is connected to your modem, but at a reduced link speed—likely 100 Mbps instead of Gigabit (1000 Mbps).
How to Fix It
This is almost always a cable issue. Unplug the Ethernet cable connecting your modem to the router's yellow Internet port. Check the connector's pins for damage. Try a different cable, and make sure it's a Cat5e or Cat6 cable. Plug it back in firmly until it clicks. The light should turn white if it negotiates a Gigabit connection.
If That Didn't Work
The port on your modem might be the issue. Try plugging the cable into a different Ethernet port on your modem, if it has one. A reboot of both the modem and router after swapping cables can also force a fresh speed negotiation.
Heads Up
If the light stays orange with a known-good cable, one of the Ethernet ports (on the router or modem) might be physically damaged and capped at 100 Mbps, which will bottleneck your entire internet connection.