Digital Certificate - password not being requested

Hi all, I have been using the Digital Certificates on Adobe Acrobrat Pro for some time and recently, I am not being prompted for my password when signing documents. I have followed the instructions here: https://helpx.adobe.com/in/acrobat/using/digital-ids.html#change_the_password_and_timeout_for_a_digital_id but have not had any luck being prompted for a password.