I've got a WHS 2011 installation with LO 1.5.3.1819
I just set up Remote Access using my Fritz!Box router and dyndns. I manually added the rules for port 80 and 443.
The remote access website of the WHS itself is showing up just fine. I can also use LightsOut using the browser interface.
I bought and installed the LightsOut WP app. When I add the dyndns url (like https://xxx.dyndns.org) and adding the usual login credentials, I always get a 404 error. The exact same URL is working in the browser.
As I saw the recommendation, I uninstalled the LO add-in on WHS, rebooted, installed it again, rebooted again - no difference.
On the LO settings, "Monitored Sources->Mobile Devices" is enabled, as is "Enable logging" and "Web Service" on the Options page. The Domain for Wake-On-Lan is set to my dyndns address.
Is there any other setting or step I missed?