Измените

 

Warning: imagepng(/var/www/mojaopstina.rs/www-root/public/images/captcha/193e629d3e9f218f7b18e5df2989e255.png): failed to open stream: Permission denied in /var/www/mojaopstina.rs/www-root/library/Zend/Captcha/Image.php on line 563