I have been having this issue for few days now. Cordova won't run in browser, error says browser is not added as a platform. However, trying to add browser as a platform, cause another error which says Unable to load platfromapi from platform. It also says that browser is not a valid platform. See screenshots:
Cordova issues 1
Cordova issues 2
Remove the platform which you try to run on it (browser, ios, android, and etc.)
cordova platform rm browser
Add the platform again
cordova platform add browser
You can run
cordova run browser
For those who's still experiencing this issue in latest ionic and cordova versions. Run:
1. ionic cordova platform rm browser/android/ios
2. ionic cordova run --emulator
It looks like the plugin PlatformApi (or what its name is exactly) is not supported by the browser platform.
You can not use the "cordova platform add browser" because the plugin was not written to work with the browser
Maybe it has some specific features that can not be emulated in the browser.