If you are getting sorry transaction failed error message on the KCB Mobile banking app when withdrawing money to mpesa or making any kind of transaction then it means that you need to update your KCB mobile app. Go to Google Play or App Store, download and install the latest version.
If you can't download the latest kcb app version because it is not supported in your mobile phone then it means you are using a mobile phone with an unsupported android version. You need to buy a new phone or upgrade to the latest android version if your phone can support it.
If updating the app does not fix your problem, you need to contact KCB customer care via phone number +254711087000 for help.