Hi,
A single Article view on Casiopea template also don't work, so problem must be from Joomla itself.
Please ask Hosting Support to recover website backup from last backup they made, X hours ago. Or use your own backup if you made yesterday.
Check also Server Error Logs.
Maybe they changed server settings in last hour(s) when you edited the site ??
It can be many reasons of that problem.
With broken SPPB page, you would have a different error message. On your site, Joomla even cannot load a template and error page. Since you are seeing Array ( [data] => ), it means that a piece of code is performing an operation on data it hasn't received (e.g., from an external API or a database). Fixing website without backup is long and expensive process.