HTML block not saving html code

Hello,
I have created a custom template "Blog Post - 1"
and I am trying to insert an HTML block,

I insert the code

<p class="lead">INTROTEXT: Lorem ipsum dolor</p>

but the block doesn't save/show it, and when I try to re-edit it, the code I have inserted is not there anymore

See also the attached image.

The block is at very beginning of the template.

Thank you

Nic