Image in signature doesn´t appear

Image in signature doesn´t appear

Hi, recently on one of the accounts under my domain, when composing an email, the image I configured on the signature stoped displaying. That happened for a couple of weeks and then it was suddenly fixed. But recently it started happening again. 

When setting up the signature and saving it, the image appears the way I want, but when I try to compose and send an email the signature appears without image.

I attach the screenshot of the Signature Settings where the image appears, and also the screen shot while composing the email, where the image does not appear. Thanks for your help.