Installing a new test project failed

The build is successful, but installing it on my android device is failing. I get the following error:

C:\Users\xxxxx\Documents\Processing\android\sdk\platform-tools\adb.exe -s V4QBB18918150321 install -r C:\Users\xxxxx\AppData\Local\Temp\android8409716540837577212sketch\app\build\outputs\apk\debug\xxxxx.apk
    status: 1

adb: failed to install C:\Users\xxxxx\AppData\Local\Temp\android8409716540837577212sketch\app\build\outputs\apk\debug\xxxxx.apk: Failure [INSTALL_FAILED_UPDATE_INCOMPATIBLE: Package package.package.package signatures do not match the previously installed version; ignoring!]
Shutting down any existing adb server... Done.

I managed to install one app, but when I tried installing another one, I got the error. I did not change the package signature between the downloads, and the package name that is displayed is the one I’m using when installing. Then I tried uninstalling the old app and the error still wouldn’t go away.

How can I fix this?