I just experienced the exact same problem today, but after some trial & error, found the problem among the network preference files.
Many unexplained process problems can arise from corrupted preferences files, that get damaged for unknown reasons. The easiest solution is to remove the corresponding preferences from the Library files (in this case, the Network preferences). After a quick restart, the system rebuilds them in the same folder.
- From Finder click Shift+Command+C, to open device folder (or Go To Apple Menu Bar > Go > Computer)
- Go To: Macintosh HD > Library > Preferences > SystemConfiguration
- Within the SystemConfiguration Folder Locate the following 3 documents:
- Select all three docs (while holding the Shift key)
- Move the 3 docs to the trash to sit (don't delete yet... just in case).
- Now Restart the computer.
- The Network should have registered the IP so Network Preferences confirms a Status: Connected, followed by the message, "Wi-Fi is connected to (router) and has the IP address xx.x.x.x".
- If not, ensure the the Turn Wi-Fi On button is clicked.