How to add colour gradient to markdown block background

Hi, I am trying to add a gradient colour background to my markdown blocks. I have the main background green in place and have tried to add the gradient by changing the code to that below, but no gradient! Thanks.

.markdown-block {
    background: linear-gradient(to right,
      #d6e6db, #e2f3e8, #d6e6db);
}

Can you share link to page where you use markdown block? We can check easier