Please can ask what devices using Android or Apple Devices?
If you're using Android Devices you need to do something called cache clear. This very easy.
If you using Apple APP then would need to delete the app reinstall it as apple don't have cache clear option.
Here's how toclearappcache: Go to the Settings menu on your device. Tap Storage. Tap "Storage" in your Android's settings. Tap Internal Storage under Device Storage... Tap Cached data. Tap OK when a dialog box appears asking if you're sure you want to clear all app cache.
If you have anymore questions don't hesitate to contact me back.
I work for Virgin Media - but all opinions posted here are my own