After making a keystore file and losing track of it, I finally discovered how to remake the keystore file and place it into the correct file i.e. One simply choses create new key in the tools/Private Sign Key window. My file is placed in: B4X/myproject/files/.keystore, etc. Now my emulator works correctly again but my phone won't display the app although the bridge seems to be correctly connected. I get the error message on the phone (B4A example window) right after it says: "Do you want to install an update to this existing application? Your data will not be lost. It does not require any special access." So I clicked install: Then it said: App not installed.