Inspite of the site itself is published correct, you got the error:
Unable to connect to Web Presence Builder server. Please contact the server administrator.
[EMERG] [System] /JsonApi/ Base_SyntaxException: PHP Warning : PDOStatement::execute(): MySQL server has gone away
Timeout defined in the
my.cnf was exceeded.
wait-timeout configuration directive in
/etc/my.cnf and restart MySQL server.