Fixed it

client/src/App.module.css

@@ -7,7 +7,6 @@
 }
 
 .header {
-  justify-self: flex-start;
   width: 100%;
   display: block;
   text-align: center;
@@ -15,7 +14,7 @@
 }
 
 .footer {
-  justify-self: flex-end;
+  bottom: 0px;
   width: 100%;
   display: block;
   text-align: center;