Update app.py

jd-webgui/app.py

@@ -157,15 +157,14 @@ def get_device():
     if devices is None:
         raise RuntimeError("MyJDownloader API returned no device list")
 
+    # sometimes devices appear with a short delay
     if not devices:
-    # Devices exist laut Server, aber noch nicht synchron
         time.sleep(2)
         jd.update_devices()
         devices = getattr(jd, "devices", []) or []
 
     if not devices:
-    raise RuntimeError("MyJDownloader connected but no devices visible yet")
-
+        raise RuntimeError("No MyJDownloader devices available (is JDownloader online/logged in?)")
 
     wanted = (MYJD_DEVICE or "").strip()
     if wanted: