I assume then that you have a system up and running with other devices? Is that system on S1 or S2? If this is pre-2015 (i.e. gen 1) Connect then it won’t be able to connect if your system is on S2.
However, its current software may just be too out-of-date for it to update without a bit of assistance. It sometimes helps to connect the unit by Ethernet while attempting the update. If that doesn’t work, Sonos support should be able to force an update through - you would need to call them if so.
Unless it has developed a fault, there is no reason why this unit should be unusable.