Europe's satellite-navigation system, Galileo, remains offline.
The network suffered an outage on Friday due to what has been described as a "technical incident related to its ground infrastructure".
Engineers worked around the clock over the weekend but there is no update yet on when the service will resume.
The problem means all receivers, such as the latest smartphone models, will not be picking up any useable timing or positional information.
These devices will be relying instead on the data coming from the American Global Positioning System (GPS).
And depending on the sat-nav chip they have installed, cell phones and other devices might also be making connections with the Russian (Glonass) and Chinese (Beidou) networks.
Galileo is still in a roll-out, or pilot phase, meaning it would not yet be expected to lead critical applications.
"People should remember that we are still in the 'initial services' phase; we're not in full operation yet," a spokesperson for the European GNSS Agency (GSA) told BBC News.
"This is something that can happen while we build the robustness into the system. We have recovery and monitoring actions, and we are implementing them, and we are working 24/7 to fix this as soon as possible."