If your asp.net versaion 2/3/3.5 website is not loading do the following
1 - Login to Plesk at https://control.vmasp.net/
2 - go to your domain name
3 - Click hosting settings
4 - scroll down and change .net version from 4.7 to 3.5 which will enable backward compatabiity for ASP.net 2 - 3.5 websites.
5 - click OK at the bottom
This will resolve your issue