One item won't "list" in store. Says Page Not Found

I have entered a couple over 100 items in the cart, and the store has been running for years.
One page comes up as Page Not Found Error 500 yet it's listed exactly the same way as other 100+ pages.

I double triple checked, deleted the item, added another successfully, tried to add this one again and it's a no go.

Anyone had similar experience?

But did not checked the error / access logs with the code error 500. May be an SEO keyword / NON UTF-8 related issue.

Thanks for the insight. I relisted using a totally, for sure, unique SEO keyword, still same thing.

My error logs latest entry is:

2018-12-10 8:25:49 - PHP Notice: A non well formed numeric value encountered in /home/ceriaton/guitarampsusa.com/catalog/controller/product/category.php on line 350

Here is line 350 from category. php

$data['results'] = sprintf($this->language->get('text_pagination'), ($product_total) ? (($page - 1) * $limit) + 1 : 0, ((($page - 1) * $limit) > ($product_total - $limit)) ? $product_total : ((($page - 1) * $limit) + $limit), $product_total, ceil($product_total / $limit));

Don't know if this helps to identify the problem. Thank you!

Scott N.

The pagination system has changed in Opencart on more recent versions. The pagination class has been switched to a controller file instead as it has been recoded. Since, it seem to be working normally.