Help with Custom Field

can you post the full code?
(if it is over 10 lines, please use the https://pastebin.com/ and follow https://codex.www.ads-software.com/Forum_Welcome#Posting_Code )

where and how have you defined $price ?

in loop-single.php

<li><span class='post-meta-key'>Price: <?php echo $Price = get_post_meta($post->ID, 'price', true); ?></span></li>

			</ul>
			</div>

<?php
if ($price == '') {
echo '<span class="band outofstock"></span>';
}
?>

you defined $Price and checked $price – variable names are case-sensitive; i.e. the spelling is important.

https://www.php.net/manual/en/language.variables.basics.php

Thanks Your a Superstar!