wordpress admin area gone

I cannot access my wordpress.org admin area for my website dStadia.com
It seems to have disappeared from my wordpress.org account, when i log in it shows dstadia and logo on the right hand side member since 2018.
but there is no admin area for the website at all.
I need to update everything, because my website is no longer resolving after I updated from php7.2 to php 7.3 and the error showing on the website is shown below.
I have tried all sorts of things including resetting my log in details to wordpress.org to get my website admin area in wordpress.org
I can log into my server and access file manager and phpmyadmin for my website.
Can anyone help me to get my admin area back and also to help me get my website to resolve online?
It appears that updating php creates this error, because of the old outdated caching sha password maybe.
I have run the database connection test many times and it always states database connection SUCCESSFUL, so all the database credentials are definitely correct.
Any help would be much appreciated.
Kind regards,
Valerie
Warning: mysqli_real_connect(): php_network_getaddresses: getaddrinfo failed: Name or service not known in /home/dstadia/public_html/wp-includes/wp-db.php on line 1653

Warning: mysqli_real_connect(): (HY000/2002): php_network_getaddresses: getaddrinfo failed: Name or service not known in /home/dstadia/public_html/wp-includes/wp-db.php on line 1653
php_network_getaddresses: getaddrinfo failed: Name or service not known

Error establishing a database connection
This either means that the username and password information in your wp-config.php file is incorrect or we can’t contact the database server at DB_HOST. This could mean your host’s database server is down.

Are you sure you have the correct username and password?
Are you sure you have typed the correct hostname?
Are you sure the database server is running?
If you’re unsure what these terms mean you should probably contact your host. If you still need help you can always visit the WordPress Support Forums.

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