Can't properly install exported APK on Android

I made a really simple 1 event project in C3 to test the export process. I exported an APK, downloaded it to my phone, tapped on it, when it asked if I wanted to install it, I said OK, and very quickly got this error: "App not installed"

Any idea what could be going wrong?

(allow external apks is enabled on my phone)

You should export as a 'debug APK'. That should work.

If you exported an unsigned APK, then you need to sign and zip align which there is a tutorial for ... which is not a simple process to initially understand. Only this type of APK can be uploaded to Google Play Store

Ah! Ok. Got it. Thanks so much.

Unfortunately I can't export anymore it just crashes