The problem you are facing because of When your application runs into a timeout on a sql database query's. It taking more than default time to return out put. So you need to increase ConnectionTimeout property.
You can do it in several ways
1. A ConnectionString has a ConnectionTimeout property. It is a property which determines the maximum number of seconds your code will wait for a connection of the database to be open. You can set connection timeout in connection string section in web.config.
<connectionstrings>
<add name="ConnectionString" connectionstring="Database=UKTST1;Server=BRESAWN;uid=" system.data.sqlclient="/><br mode=" hold=" /><br mode=" html="> <asp:ToolkitScriptManager runat=" server=" AsyncPostBackTimeOut=" 6000="><br mode="></add></connectionstrings>
2. You can put AsyncPostBackTimeout="6000" in .aspx page
<asp:ToolkitScriptManager runat="server"; AsyncPostBackTimeOut="6000";
</asp:ToolkitScriptManager>
3. You can set timeout in sqlcommand where you are calling storeprocedure in .cs file.
command.CommandTimeout = 30*1000;
hope you have got solution.