I also have this same issue. I am running web remote 1.2.4. I have another location that that is running web remote 1.1.0. It seams to work. Don't know if the updated version is the issue? can I install an older version of web remote to test, and if so how?
Ok... after more testing I have never be able get the slides to display through the web remote at .../main.
When I connect NDI Tools Screen capture, as I cycle through the slides sometimes some of the slides will appear and sometimes the windows desktop shows. It is not the same slides that show, random, shows one time, desktop the next time... maybe a timing problem?