RegEx validator doesn't display message

[Jinspire]

Hello, everyone!

I have a the following regular expression validator:

<asp:RegularExpressionValidator ID="revTime" runat="server" ControlToValidate="txtTime"
ErrorMessage="Time interval must be between 00:00 and 23:59"
ValidationExpression="(^0{0,1}\d:[0-5]\d{0,1}$)|(^[0,1]\d:[0-5]\d(0,1)$)|(^2[0-3]:[0-5]\d(0,1)$)"
Display="Dynamic" />

The validator WORKS. The regular expression works too.

Problem is, the message does not display.

I've tried the following:
* Changing the Display attribute to "Static" or "None";
* Using the Text attribute instead of ErrorMessage;
* Playing around with EnableClientScript (oddly enough, when I set it to "false," the message is displayed, but the validator doesn't prevent submission);
* Banging my head against the table (this actually helps sometimes).

The strangest thing is that I copy-pasted the validator from another page in the project (yes, I renamed the ID and the ControlToValidate!), where the validator works perfectly.
Why does it act differently on this page?

[kvprajapati]

Try this,

<asp:RegularExpressionValidator ID="revTime" 
                                runat="server" ControlToValidate="txtTime"
                                ErrorMessage="Time interval must be between 00:00 and 23:59"
                                ValidationExpression="^(?:0?[0-9]|1[0-9]|2[0-3]):[0-5][0-9]$"
                                Display="Dynamic" />

[Jinspire]

Thanks for the reply.

There's no problem with the ValidationExpression; it validates the format as it should, and prevents the page from being submitted to the server unless txtTime is inputed correctly.

The problem is the message which simply doesn't show.