Drupal 8.x

I am having a drupal application to connects to database in a diffrent server. The database had some issues but we managed to restore it. When trying to access the application it pops up the drupal installation dialog. I haven't changed the database connection details in setting.php file. What could be the issue?

I need to implement one of the following options, if possible:
A) Make the BUY button only send an email or...
B) When processing the cart items, only an email to be sent about the purchased items.

I don't need a real credit card purchase on the site, once we get the email we can process the items manually.
This is for an organization that don't sell items but gives them away.

Any suggestion would be appreciated.

Hi can someone help me with this?

The website encountered an unexpected error. Please try again later.
Error: Wrong parameters for Drupal\msg_mailup\Plugin\Mailup\MailUpException([string $message [, long $code [, Throwable $previous = NULL]]]) in Exception->__construct() (line 111 of modules/contrib/msg_mailup/src/Plugin/Mailup/MailUpClientRest.php).