Pixel 2, Android 8.1.0
I have an .apk which has been signed by a developer on our team. The first time I install one of the builds, it installs fine. If I uninstall the app and try to reinstall it again from the .apk, this is what happens:
I have tried clearing the data/cache of the Package Installer app as has been suggested elsewhere on google, but it did not help.
I should note that I am not an android developer, and our android developer does not know what's causing this or how to fix it. He is also a remote dev, so I can't just have him come have a look. I am not able to physically connect my phone to my computer, as it is a USB-C phone and I don't have a USB-C => USB-A cable.
EDIT As requested in the comments, I am uninstalling the app by long-tapping the appicon and dragging it to the top of the screen where it says "uninstall". I have also tried uninstalling it from the app settings to the same effect (Settings -> Apps & notifications -> -> Uninstall)