Server-level issue when changing template

I’m working on a Joomla remake. I’m trying to change the pattern. When changing the header .tpl file (changes in the body), any page returns an empty result. At the same time, the same content integrated into the required template at the .html level is displayed normally. error_reporting(1); on the required page and the analogue in .htaccess did not help, it does not display an error. Paste code –
How to fix?

Answer 1

Didn’t work with Joomla, but as far as I know, *.tpl files are compiled templates… (in Smarty for sure). So, the compiled template differs from the usual html file in that it is not rendered directly to the browser, but is first compiled. Also for template files (based on Smarty) a special syntax is used. Pieces of javascript code in such templates need to be isolated.

Smarty example again

<script type="text/javascript">
  function isblank(field) {
    if (field.value == '')
      { return false; }
      return true;

Try digging this way…