Mt Start 25 satnav has been constantly 'waiting for a valid GPS signal' these past few weeks, which I assumed to be a WNRO issue which would be fixed by an update. So today I installed the two core updates, but this has not fixed the issue. The TomTom website also said to check that the device's battery is fully charged, but how do you do that? - there's no virtual button I can find that will give's me the battery status, so should I leave it connect it to my computer for 5 hours and then assume it's fully charged? What if the battery is not retaining its charge any more? - how do I know if that's the case? Is it possible to change the battery? (the Start 25 appears to be a sealed unit). OK, the unit is a few years old now but it was working perfectly until early April 2019.