Build android ARCore ERROR

Hello!! I am getting this error and can not make a build for android phone. I am using unity 2019.3.7 I use the git hub examples of image tracker

Failed to generated ARCore reference image library 'ReferenceImageLibrary' UnityEngine.GUIUtility:ProcessEvent(Int32, IntPtr)

BuildFailedException: Failed to generate image database. Output from arcoreimg:

stdout:

====

stderr: Assets/Opuscardpng.png: Failed to get enough keypoints from target image.Failed to add some of the images to database. ==== UnityEditor.XR.ARCore.ARCorePreprocessBuild.BuildImageTrackingAssets () (at Library/PackageCache/com.unity.xr.arcore@4.0.0-preview.1/Editor/ARCoreBuildProcessor.cs:312) UnityEditor.XR.ARCore.ARCorePreprocessBuild.OnPreprocessBuild (UnityEditor.Build.Reporting.BuildReport report) (at Library/PackageCache/com.unity.xr.arcore@4.0.0-preview.1/Editor/ARCoreBuildProcessor.cs:34) UnityEditor.Build.BuildPipelineInterfaces+<>c_DisplayClass15_0.b_1 (UnityEditor.Build.IPreprocessBuildWithReport bpp) (at :0) UnityEditor.Build.BuildPipelineInterfaces.InvokeCallbackInterfacesPair[T1,T2] (System.Collections.Generic.List`1[T] oneInterfaces, System.Action`1[T] invocationOne, System.Collections.Generic.List`1[T] twoInterfaces, System.Action`1[T] invocationTwo, System.Boolean exitOnFailure) (at :0) UnityEngine.GUIUtility:ProcessEvent(Int32, IntPtr)

Can anyone help me with this!?