Greetings,
we’ve experienced a problem with the database connection error that appears more and more frequently.
We don’t know the cause. The theme was installed on a clone of the old website which was renamed into https://old.solipapar.com and the main page in production is https://solipapar.com
The thing is that the error is not showing the code from the theme files. So first please, check how it works with some default WordPress themes like TwentyTwenty Five or WooCommerce Storefront to understand if it is our theme issue or not.