[cred_delete_post_link action="trash" text="Delete %TITLE%" message_after="Post deleted" message="Are you sure you want to delete this post?" message_show="1"]
I just checked on my local test site and inserted the delete shortcode via the Toolset Forms button in a Fields and Text block, and it worked when testing on the front end.
The shortcode generated was
[cred-delete-post action='trash' onsuccess='self']Delete this post[/cred-delete-post]
Based on the options I chose when inserting the shortcode, clicking the Delete button submits a request that results in the post being trashed, and the same page reloading.
My example is in the loop output of a View (screenshot).
The problem on your site, it looks to me like you are adding the shortcode to the link section of a button. If you just add the shortcode to a Shortcode block so that you can inspect the generated output on the front end, you'll see that it outputs an anchor element. The link section of a button would generate an anchor element, so you might be trying to add an anchor element within an anchor element, which would be invalid HTML and would not work.
In which case you would need to use something other than a button block, possibly hand-crafting the HTML to provide the same markup for the button with your link coming from the shortcode.