Hello Sandra,

The ALT attribute for images does show if you enter it.

I just tested it on our development site.

When adding a featured image to a post make sure to enter something in the proper field.

See here https://www.dropbox.com/s/gppc6rvk2gz2cm1/image-alt-text.PNG?dl=0

Then when you look at the source code for the page you will see the ALT attribute is there.