I saw this error message in the log file of Apache
[Tue Dec 04 18:54:37.415520 2018] [proxy_fcgi:error] [pid 1796:tid 140266887427840] [client 126.96.36.199:58963] AH01071: Got error 'PHP message: PHP Fatal error: Class 'WC_Integration' not found in /opt/bitnami/apps/wordpress/htdocs/wp-content/plugins/woocommerce-shipstation-integration/includes/class-wc-shipstation-integration.php on line 10\n'
You can learn how to debug Apache's issues by following this guide
I suggest you disable all the WordPress plugins and start enabling them after that. You can rename the plugins folder to disable all of them at the same time
sudo mv /opt/bitnami/apps/wordpress/htdocs/wp-content/plugins /opt/bitnami/apps/wordpress/htdocs/wp-content/plugins.back
Happy to help!
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