So, you've written a new message, or opened an old message to reply or forward it?

You have typed some text?

Is there a modal dialog window lurking in the background that needs you to deal with it first? Try alt+tab to cycle through open windows.

When I press reply there is no problem , only in new message somehow I cannot send a new message ?

When you first open a new Write message, the 'Send' button should be subdued or look like it is greyed out and you cannot click on it.

It will not appear as useable until you have entered the TO field email addresses, because without knowing where to send to, it cannot send.

So, confirm that you have actually added the TO/Cc/Bcc email addresses.

So why is it auto enabled when you click on eg: Reply? Because the TO fields are auto completed.

thanks for this you have answered my question, its working now.