Измените

 

Warning: imagepng(/var/www/mojaopstina.rs/www-root/public/images/captcha/a88b1c6e623c4ad9f40dda8d18aad330.png): failed to open stream: Permission denied in /var/www/mojaopstina.rs/www-root/library/Zend/Captcha/Image.php on line 563