Index: wp-content/themes/twentynineteen/sass/blocks/_blocks.scss
===================================================================
--- wp-content/themes/twentynineteen/sass/blocks/_blocks.scss	(revision 53921)
+++ wp-content/themes/twentynineteen/sass/blocks/_blocks.scss	(working copy)
@@ -1046,3 +1046,12 @@
 		color: #FFF;
 	}
 }
+
+// Tag Cloud
+.wp-block-tag-cloud {
+
+	&.aligncenter {
+		text-align: center;
+		justify-content: center;
+	}
+}
Index: wp-content/themes/twentynineteen/style-editor.scss
===================================================================
--- wp-content/themes/twentynineteen/style-editor.scss	(revision 53921)
+++ wp-content/themes/twentynineteen/style-editor.scss	(working copy)
@@ -995,3 +995,13 @@
 		width: 100%;
 	}
 }
+
+
+// Tag Cloud
+.wp-block-tag-cloud {
+
+	&.aligncenter {
+		text-align: center;
+		justify-content: center;
+	}
+}	
Index: wp-content/themes/twentytwentyone/assets/sass/05-blocks/tag-clould/_editor.scss
===================================================================
--- wp-content/themes/twentytwentyone/assets/sass/05-blocks/tag-clould/_editor.scss	(revision 53921)
+++ wp-content/themes/twentytwentyone/assets/sass/05-blocks/tag-clould/_editor.scss	(working copy)
@@ -2,5 +2,6 @@
 
 	&.aligncenter {
 		text-align: center;
+		justify-content: center;
 	}
 }