Unable to merge android manifests MAC

Please help!
I've tried everything I could but this issue doesn't get solved.
I've checked all the Q/A I could find on google, still couldn't solve this.

When I click Build or Build and Run it says "Unable to merge android manifests" I'm trying to build apk for android.

Here are issues in as listed in the console.

Issue 1.

 Error: Error while saving blame file, build will continue
 Error: The prefix "tools" for attribute "tools:ignore" associated with an 
 element type "activity" is not bound.

 UnityEngine.GUIUtility:ProcessEvent(Int32, IntPtr)

issue 2.

 AndroidSDKToolsException: Unable to merge android manifests. 
 UnityEditor.Android.AndroidSDKTools.DetectErrorsAndWarnings (System.String logMessages, System.String errorMsg)
 UnityEditor.Android.AndroidSDKTools.RunCommandInternal (System.String javaExe, System.String sdkToolsDir, System.String[] sdkToolCommand, Int32 memoryMB, System.String workingdir, UnityEditor.Android.WaitingForProcessToExit waitingForProcessToExit, System.String errorMsg)
 UnityEditor.Android.AndroidSDKTools.RunCommand (System.String javaExe, System.String sdkToolsDir, System.String[] sdkToolCommand, Int32 memoryMB, System.String workingdir, UnityEditor.Android.WaitingForProcessToExit waitingForProcessToExit, System.String errorMsg)
 UnityEditor.Android.AndroidSDKTools.RunCommand (System.String[] sdkToolCommand, UnityEditor.Android.WaitingForProcessToExit waitingForProcessToExit, System.String errorMsg)
 UnityEditor.Android.AndroidSDKTools.MergeManifests (System.String target, System.String mainManifest, System.String[] libraryManifests, UnityEditor.Android.WaitingForProcessToExit waitingForProcessToExit)
 UnityEditor.Android.PostProcessor.Tasks.GenerateManifest.MergeManifests (UnityEditor.Android.PostProcessor.PostProcessorContext context, System.String mainManifest, System.String targetManifest)
 UnityEditor.Android.PostProcessor.Tasks.GenerateManifest.Execute (UnityEditor.Android.PostProcessor.PostProcessorContext context)
 UnityEditor.Android.PostProcessor.PostProcessRunner.RunAllTasks (UnityEditor.Android.PostProcessor.PostProcessorContext context)
 UnityEngine.GUIUtility:ProcessEvent(Int32, IntPtr)

issue 3.

 Build completed with a result of 'Failed'
 UnityEngine.GUIUtility:ProcessEvent(Int32, IntPtr)

issue 4.

 UnityEditor.BuildPlayerWindow+BuildMethodException: 3 errors
   at UnityEditor.BuildPlayerWindow+DefaultBuildMethods.BuildPlayer (BuildPlayerOptions options) [0x0021f] in /Users/builduser/buildslave/unity/build/Editor/Mono/BuildPlayerWindowBuildMethods.cs:182 
   at UnityEditor.BuildPlayerWindow.CallBuildMethods (Boolean askForBuildLocation, BuildOptions defaultBuildOptions) [0x00065] in /Users/builduser/buildslave/unity/build/Editor/Mono/BuildPlayerWindowBuildMethods.cs:89 
 UnityEngine.GUIUtility:ProcessEvent(Int32, IntPtr)

Things I have done/tried: (still hasn't solved the problem)
Downloaded every sdk (API level) 10,11,all the way to 27 through Android studio SKD manager.
I've tried changing sdk through player preferences in unity, also tried changing SDK version of manifist file (mine currently says minsdk 15). Also tried copying AndroidManifest file from temp/StagingArea to Assets/Plugins/Android,, still didn't work.

Really appreciate your help,
Thanks!