Please note that we do not support issues coming from customizations even if we provided the guide previously because it is not sustainable. Future advancements in the code usually break the custom code and it requires development time to fix that which is not a part of our support service. Custom code suggestions also are catered to those who are comfortable with coding. It was meant to get such users a starting point. Custom codes were not meant to be maintained by us.
If you're not a developer or do not want to deal with coding including maintainance, what I'd recommend you to do is to remove the custom template or switch to the parent theme and use one of the bundled grid plugins for your Portfolio. You can choose between the The Grid and Essential Grid. Those plugins were bundled to give our users more options to display posts, portfolios and custom post types listing that are not offered in the theme.
If the issue persists using the parent theme, please test for a plugin conflict. You can do this by deactivating all third party plugins, and seeing if the problem remains. If it's fixed, you'll know a plugin caused the problem, and you can narrow down which one by reactivating them one at a time.
Still if the issue persists using the parent theme, try reinstalling WordPress by going to Dashboard > Updates.
Thank you for understanding.