Hello,
The service log file, erroglog.txt, can be found in Program Files (x86)\Lansweeper\Service\. You can also consult the web_errorlog.txt in Program Files (x86)\Lansweeper\Website\App_Data\.
If the application opens fine under localhost, there won't be a problem with Lansweeper itself. Depending on the url you are using to open the application, there will be most likely an issue to resolve the name of the server or IP from the client you are using in the url.