Extracting the duration from different rows

Still working fine with me.

Maybe you can verify - Edit: in the Query Editor at step #"Added Custom4" - with the code below (adjust for your source) in which I created separate columns for each condition that must all be TRUE for the duration to be calculated. If at least one of the conditions is FALSE, Duration will be null.

let
    Source = Excel.CurrentWorkbook(){[Name="Table1"]}[Content],
    #"Changed Type" = Table.TransformColumnTypes(Source,{{"Date", type date}, {"Time", type time}, {"Action", type text}, {"Service", type text}, {"User", type text}, {"Server", type text}}),
    #"Inserted Merged Date and Time" = Table.AddColumn(#"Changed Type", "DateTime", each [Date] & [Time], type datetime),
    #"Added Index" = Table.AddIndexColumn(#"Inserted Merged Date and Time", "Original Sort", 0, 1),
    #"Sorted Rows" = Table.Sort(#"Added Index",{{"User", Order.Ascending}, {"Service", Order.Ascending}, {"DateTime", Order.Ascending}}),
    #"Added Index1" = Table.AddIndexColumn(#"Sorted Rows", "Index", 0, 1),
    #"Added Index2" = Table.AddIndexColumn(#"Added Index1", "Index.1", 1, 1),
    #"Merged Queries" = Table.NestedJoin(#"Added Index2",{"Index"},#"Added Index2",{"Index.1"}, "Previous",JoinKind.LeftOuter),
    #"Expanded Previous" = Table.ExpandTableColumn(#"Merged Queries", "Previous", {"Action", "User", "Service", "DateTime"}, {"Previous.Action", "Previous.User", "Previous.Service", "Previous.DateTime"}),
    #"Added Custom" = Table.AddColumn(#"Expanded Previous", "CheckUser", each [User] = [Previous.User]),
    #"Added Custom1" = Table.AddColumn(#"Added Custom", "CheckService", each [Service] = [Previous.Service]),
    #"Added Custom2" = Table.AddColumn(#"Added Custom1", "CheckOut", each [Action] = "OUT"),
    #"Added Custom3" = Table.AddColumn(#"Added Custom2", "CheckIn", each [Previous.Action] = "IN"),
    #"Added Custom4" = Table.AddColumn(#"Added Custom3", "Duration", each if [CheckUser] and [CheckService] and [CheckOut] and [CheckIn] then [DateTime] - [Previous.DateTime] else null),
    #"Sorted Rows1" = Table.Sort(#"Added Custom4",{{"Original Sort", Order.Ascending}}),
    #"Removed Other Columns" = Table.SelectColumns(#"Sorted Rows1",{"DateTime", "Action", "Duration", "User", "Service", "Server"})
in
    #"Removed Other Columns"