Unity won't build on android after integrating Chartboost [Unable to Determine which Android Packages are installed]

I am at a loss. I am a complete noob when it comes to android development and such and all my Unity and programming knowledge comes from youtube and tutorials. I have this mind numbing problem where unity 2019.3 would work a night before and the next morning it won't build. I keep getting the same error

I got around the problem by resetting my windows and installing Unity 2019.3.6f1 with Android support + SDK + NDK from Unity Hub. It did allow me to build one of my projects but an older project still kept on giving me this error. So I Installed Unity 2019.3.0 with Android support + SDK + NDK and now everything is broken again. The 2019.3.6f1 started giving me this error even on the project that I had built on it successfully. I have been facing this problem for more than 2 weeks now and it is seriously affecting my progress. I removed the older unity version but the error still persists. I have looked everywhere on the internet but no one seems to have this specific problem with Unity. The only answers that are available are of Android Studio and Firebase of which I don't know a single thing about. Please help.