diff --git src/bp-activity/bp-activity-cssjs.php src/bp-activity/bp-activity-cssjs.php
index 26748b440..40989577c 100644
--- src/bp-activity/bp-activity-cssjs.php
+++ src/bp-activity/bp-activity-cssjs.php
@@ -22,10 +22,16 @@ function bp_activity_mentions_script() {
 
 	// Special handling for New/Edit screens in wp-admin.
 	if ( is_admin() ) {
+		$current_screen = null;
+		if ( function_exists( 'get_current_screen' ) ) {
+			$current_screen = get_current_screen();
+		}
+
 		if (
-			! get_current_screen() ||
-			! in_array( get_current_screen()->base, array( 'page', 'post' ) ) ||
-			! post_type_supports( get_current_screen()->post_type, 'editor' ) ) {
+			! $current_screen ||
+			( isset( $current_screen->is_block_editor ) && $current_screen->is_block_editor ) ||
+			! in_array( $current_screen->base, array( 'page', 'post' ) ) ||
+			! post_type_supports( $current_screen->post_type, 'editor' ) ) {
 			return;
 		}
 	}
diff --git src/bp-templates/bp-nouveau/includes/activity/widgets.php src/bp-templates/bp-nouveau/includes/activity/widgets.php
index 7097519d9..206c2d7bc 100644
--- src/bp-templates/bp-nouveau/includes/activity/widgets.php
+++ src/bp-templates/bp-nouveau/includes/activity/widgets.php
@@ -3,7 +3,7 @@
  * BP Nouveau Activity widgets
  *
  * @since 3.0.0
- * @version 3.1.0
+ * @version 8.0.0
  */
 
 // Exit if accessed directly.
@@ -80,14 +80,18 @@ class BP_Latest_Activities extends WP_Widget {
 		 */
 		$title = apply_filters( 'widget_title', $title, $instance, $this->id_base );
 
-		// Check instance for custom max number of activities to display
+		// Check instance for custom max number of activities to display.
 		if ( ! empty( $instance['max'] ) ) {
 			$max = (int) $instance['max'];
 		}
 
-		// Check instance for custom activity types
+		// Check instance for custom activity types.
 		if ( ! empty( $instance['type'] ) ) {
-			$type    = maybe_unserialize( $instance['type'] );
+			$type = maybe_unserialize( $instance['type'] );
+			if ( ! is_array( $type ) ) {
+				$type = (array) maybe_unserialize( $type );
+			}
+
 			$classes = array_map( 'sanitize_html_class', array_merge( $type, array( 'bp-latest-activities' ) ) );
 
 			// Add classes to the container
@@ -181,6 +185,9 @@ class BP_Latest_Activities extends WP_Widget {
 		$type = array( 'activity_update' );
 		if ( ! empty( $instance['type'] ) ) {
 			$type = maybe_unserialize( $instance['type'] );
+			if ( ! is_array( $type ) ) {
+				$type = (array) maybe_unserialize( $type );
+			}
 		}
 		?>
 		<p>