Mac Pro won't connect to Ethernet

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My Mac Pro will not connect to the internet, but it connects to Wifi via my comcast modem.
the modem was switched out today, but I couldn't connect before that - which is why they came and replaced my modem.
The lights in the Diagnostics window say:
Ethernet: connected
Wifi: connected
ISP: Fail
Internet: Fail
Server: Fail
Any ideas?
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Replay

Boot into Recovery by holding down the key combination command-R at the startup chime. Release the keys when you see a gray screen with a spinning dial.
Note: You need an always-on Ethernet or Wi-Fi connection to the Internet to use Recovery. It won’t work with USB or PPPoE modems, or with proxy servers, or with networks that require a certificate for authentication.
From the OS X Utilities screen, select Get Help Online. A clean copy of Safari will launch. No plugins, such as Flash, will be available. While in Recovery, you'll have no access to your saved bookmarks or passwords, so make a note of those before you begin, if they're needed for the test.
Test. After testing, reboot as usual and post the results.