Fufill ONLY with ''False''

Well, it's only updating the ClickOut column because you've overwritten the other two UPDATE statements.

You need to call ExecuteNonQuery after each one:

comm.CommandText = "UPDATE 1 SET Absent='Ausente' WHERE ISNULL(Absent) OR Absent='True'";
comm.ExecuteNonQuery();

comm.CommandText = "UPDATE 1 SET clock_In='Ausente' WHERE ISNULL(clock_In) OR clock_In=''";
comm.ExecuteNonQuery();

comm.CommandText = "UPDATE 1 SET clock_Out='Ausente' WHERE ISNULL(clock_Out) OR clock_Out=''";
comm.ExecuteNonQuery();

The columns name was wrong. But I correct it now.
But when click the message error doesnt appear. Its update only the clock_out column. What happen?

@Vulpe
This is one of the very importante code for me to learn.
Firstly for what I need to do I do put it in the load event. But what kind of problem I meet now.  Unfortunatly it's doesnt react (no error message... no buggs). 
Then I do drop here the whole code. But its gives this message: A operação tem que utilizar uma consulta actualizável:

            conn.Close(); 

Then an idea cames to me. I do try to do this for updating multiple values (for example 3). But doesnt works. How can I resolv that:
I try this:

UPDATE MyTable SET Absent='False'  and clickIn='False' and clickOut='False' WHERE ISNULL(Absent, ClickIn, ClickOut) OR Absent='' OR ClickIn='' OR ClickOut;