diff --git a/auth/src/main/java/org/openedx/auth/presentation/signin/SignInViewModel.kt b/auth/src/main/java/org/openedx/auth/presentation/signin/SignInViewModel.kt
index 395cf7ec5..e7053f2c6 100644
--- a/auth/src/main/java/org/openedx/auth/presentation/signin/SignInViewModel.kt
+++ b/auth/src/main/java/org/openedx/auth/presentation/signin/SignInViewModel.kt
@@ -34,6 +34,7 @@ import org.openedx.core.system.notifier.app.AppUpgradeEvent
 import org.openedx.core.system.notifier.app.SignInEvent
 import org.openedx.core.utils.Logger
 import org.openedx.foundation.presentation.BaseViewModel
+import org.openedx.foundation.presentation.UIMessage
 import org.openedx.foundation.system.ResourceManager
 import org.openedx.core.R as CoreRes
 
@@ -217,7 +218,23 @@ class SignInViewModel(
             interactor.loginSocial(token, authType)
         }.onFailure { error ->
             logger.e { "Social login error: $error" }
-            onUnknownError()
+            if (error is EdxError.InvalidGrantException) {
+                // The social identity resolved on Google's side but is not linked to any
+                // account on this platform. The mobile token-exchange endpoint only signs in
+                // existing/linked users, so guide the user to register (mirrors iOS/web).
+                sendMessage(
+                    UIMessage.SnackBarMessage(
+                        resourceManager.getString(
+                            R.string.auth_social_account_not_registered,
+                            authType.methodName,
+                            configuration.getPlatformName(),
+                        )
+                    )
+                )
+                _uiState.update { it.copy(showProgress = false) }
+            } else {
+                onUnknownError()
+            }
         }.onSuccess {
             logger.d { "Social login (${authType.methodName}) success" }
             _uiState.update { it.copy(loginSuccess = true) }
diff --git a/auth/src/main/java/org/openedx/auth/presentation/sso/GoogleAuthHelper.kt b/auth/src/main/java/org/openedx/auth/presentation/sso/GoogleAuthHelper.kt
index 99985b882..c5e2ced6e 100644
--- a/auth/src/main/java/org/openedx/auth/presentation/sso/GoogleAuthHelper.kt
+++ b/auth/src/main/java/org/openedx/auth/presentation/sso/GoogleAuthHelper.kt
@@ -105,6 +105,20 @@ class GoogleAuthHelper(private val config: Config) {
 
     private companion object {
         const val TAG = "GoogleAuthHelper"
-        const val SCOPE = "oauth2: https://www.googleapis.com/auth/userinfo.email"
+
+        /**
+         * Scopes requested for the Google access token that is exchanged on the backend via
+         * `/oauth2/exchange_access_token/google-oauth2/`.
+         *
+         * Must match the scopes expected by the server-side social-auth `google-oauth2` backend
+         * (`DEFAULT_SCOPE = ["openid", "email", "profile"]`) and the iOS/web clients. Requesting
+         * only `userinfo.email` yields a token whose `userinfo` response lacks the profile/name
+         * claims, so first-time SSO account creation fails and the exchange returns
+         * `invalid_grant` ("access_token is not valid"). The `oauth2:` prefix is immediately
+         * followed by a space-separated scope list (no leading space).
+         */
+        const val SCOPE = "oauth2:openid " +
+            "https://www.googleapis.com/auth/userinfo.email " +
+            "https://www.googleapis.com/auth/userinfo.profile"
     }
 }
diff --git a/auth/src/main/res/values/strings.xml b/auth/src/main/res/values/strings.xml
index 77401c27f..9838dab6b 100644
--- a/auth/src/main/res/values/strings.xml
+++ b/auth/src/main/res/values/strings.xml
@@ -10,6 +10,7 @@
     <string name="auth_email_username" tools:ignore="MissingTranslation">Email or Username</string>
     <string name="auth_invalid_email_username" tools:ignore="MissingTranslation">Invalid email or username</string>
     <string name="auth_invalid_password">Password is too short</string>
+    <string name="auth_social_account_not_registered">This %1$s account is not linked with any %2$s account. Please register.</string>
     <string name="auth_welcome_back">Welcome back! Sign in to access your courses.</string>
     <string name="auth_show_optional_fields">Show optional fields</string>
     <string name="auth_hide_optional_fields">Hide optional fields</string>