I have a problem with my flutter application,

My app is running normally but when i added onesignal notification plugin, i got the error below :

What went wrong: A problem occurred configuring project ':firebase_admob'. > Could not resolve all artifacts for configuration ':firebase_admob:classpath'. > Could not find any matches for gradle.plugin.com.onesignal:onesignal-gradle-plugin:[0.12.4, 0.99.99] as no versions of gradle.plugin.com.onesignal:onesignal-gradle-plugin are available

I searched many times on google and no solution found. after many tests on new cleaned flutter app.

I've found the error, it was in Pubspec.yaml

when i remove

firebase_admob: ^0.9.0+7

in dependencies: it solved but when i add it, I got the error above.

PS : I created new flutter application and working on it to remove that stucked error.

when i configure the onesignal it will show errors as below :

ERROR: Could not find any matches for gradle.plugin.com.onesignal:onesignal-gradle-plugin:[0.12.4, 0.99.99] as no versions of gradle.plugin.com.onesignal:onesignal-gradle-plugin are available. Searched in the following locations: - dl.google.com/dl/android/maven2/gradle/plugin/com… - dl.google.com/dl/android/maven2/gradle/plugin/com… - jcenter.bintray.com/gradle/plugin/com/onesignal/o… - jcenter.bintray.com/gradle/plugin/com/onesignal/o… Required by: project :

Please help..?