emailing invoices on starting point

i am having a problem with the email function on invoice tab within 'starting point' when i hit 'email invoice' it should set up an email with the invoice as an attached item however it doesn't, when i do the same within the 'estimates' tab it pops up with my email from an attaches the estimate and i can send it to the client 

so recap emailing estimates works but trying to email invoices it won't provide me with an option to 'send' 

help ?

it did work but now doesn't......

thanks on advance