Index: wordpress.org/public_html/wp-content/plugins/plugin-directory/api/routes/class-plugin-committers.php
===================================================================
--- wordpress.org/public_html/wp-content/plugins/plugin-directory/api/routes/class-plugin-committers.php	(revision 5928)
+++ wordpress.org/public_html/wp-content/plugins/plugin-directory/api/routes/class-plugin-committers.php	(working copy)
@@ -91,7 +91,18 @@
 
 	function add_committer( $request ) {
 		$user = new WP_User( $request['committer'] );
-		if ( ! $user->exists() ) {
+
+		// If user_login is not found, try searching by user_nicename.
+		if ( ! $user || ! $user->exists() ) {
+			$user = get_user_by( 'slug', $request['committer'] );
+		}
+
+		// If user_nicename is not found, try searching by user_email.
+		if ( ! $user || ! $user->exists() ) {
+			$user = get_user_by( 'email', $request['committer'] );
+		}
+
+		if ( ! $user || ! $user->exists() ) {
 			return new WP_Error( 'plugin_user_not_found', __( 'The provided user could not be found.', 'wporg-plugins' ) );
 		}
 
@@ -106,7 +117,18 @@
 
 	function revoke_committer( $request ) {
 		$user = new WP_User( $request['committer'] );
-		if ( ! $user->exists() ) {
+
+		// If user_login is not found, try searching by user_nicename.
+		if ( ! $user || ! $user->exists() ) {
+			$user = get_user_by( 'slug', $request['committer'] );
+		}
+
+		// If user_nicename is not found, try searching by user_email.
+		if ( ! $user || ! $user->exists() ) {
+			$user = get_user_by( 'email', $request['committer'] );
+		}
+
+		if ( ! $user || ! $user->exists() ) {
 			return new WP_Error( 'plugin_user_not_found', __( 'The provided user could not be found.', 'wporg-plugins' ) );
 		}
 
Index: wordpress.org/public_html/wp-content/plugins/plugin-directory/api/routes/class-plugin-support-reps.php
===================================================================
--- wordpress.org/public_html/wp-content/plugins/plugin-directory/api/routes/class-plugin-support-reps.php	(revision 5928)
+++ wordpress.org/public_html/wp-content/plugins/plugin-directory/api/routes/class-plugin-support-reps.php	(working copy)
@@ -91,7 +91,18 @@
 
 	function add_support_rep( $request ) {
 		$user = new WP_User( $request['support_rep'] );
-		if ( ! $user->exists() ) {
+
+		// If user_login is not found, try searching by user_nicename.
+		if ( ! $user || ! $user->exists() ) {
+			$user = get_user_by( 'slug', $request['support_rep'] );
+		}
+
+		// If user_nicename is not found, try searching by user_email.
+		if ( ! $user || ! $user->exists() ) {
+			$user = get_user_by( 'email', $request['support_rep'] );
+		}
+
+		if ( ! $user || ! $user->exists() ) {
 			return new WP_Error( 'plugin_user_not_found', __( 'The provided user could not be found.', 'wporg-plugins' ) );
 		}
 
@@ -106,7 +117,18 @@
 
 	function remove_support_rep( $request ) {
 		$user = new WP_User( $request['support_rep'] );
-		if ( ! $user->exists() ) {
+
+		// If user_login is not found, try searching by user_nicename.
+		if ( ! $user || ! $user->exists() ) {
+			$user = get_user_by( 'slug', $request['support_rep'] );
+		}
+
+		// If user_nicename is not found, try searching by user_email.
+		if ( ! $user || ! $user->exists() ) {
+			$user = get_user_by( 'email', $request['support_rep'] );
+		}
+
+		if ( ! $user || ! $user->exists() ) {
 			return new WP_Error( 'plugin_user_not_found', __( 'The provided user could not be found.', 'wporg-plugins' ) );
 		}