Build Settings interface is different after reimporting assets,something wrong with build settings after reimporting all assets

Forgive me if theres a simple solution to this (as I'm just a beginner), but I've come across this problem after trying to get Unity Remote 5 to work. Looking across the forums, I found an answer that said to "reimport all assets", and I did that - however, upon opening it back upon again and going to Build Settings for Android, all of the original settings were replaced by a grey screen with checkboxes that I couldn't change.

As you can see, there isn't an option to "build and run", and the normal interface is completely different now. Again, I can't change any of these settings, and I'm not sure what the problem (or solution) could be. Any help would be greatly appreciated.

Thanks, everyone!