ASP.NET session timeout for the site is set to 60 minutes in
**Plesk Control Panel->domains->domain.tld->ASP.NET settings** , however client's script times out within 5-10 minutes.
Application Pool Idle Timeout can affect script timeout.
Application Pool Idle Timeout in IIS->Application pools->domain application pool->Properties->Idle Time-out .
Also it may require to set additional timeout in IIS->Website->domain.tld->Session State->TimeOut .
For additional information and code examples please refer to the Official Microsoft IIS Site