Can't Search and replace Regex

Hi,

Using Calibre's Editor I can see the following code:

<p class="noindent"><span class="txbdit">SOME TEXT</span>

I want to change all instances to h4

<h4>SOME TEXT</h4>

I've used

Mode: Regex Wrap checked, Dot all, checked

It keeps saying, "0 Replacements"

I've tried the following syntaxes:

<p class="noindent"><span class="txbdit">(.*?)</span>

<h4>$1</h4>


<p class="noindent"><span class="txbdit">.*?</span>

<h4>$1</h4>


AS WELL AS
<p\s+class="noindent"><span\s+class="txbdit">.*? </span>

<p\s*class="noindent"\s*><span\s*class="txbdit"\s* >.*?</span>


INTERESTINGLY
I cannot search or replace even

<p>
<h4>

But, searching and replacing for

<p class="noindent">
Pericles

Works.

What do you think is happening?

https://ibb.co/Lkj9KKN