According to the configuration of MySQl and the Wordpress version, it is possible that you cannot create new post on the admin side because the database does not accept dates where all fields are 0, it is what Wordpress provides temporarily.
To solved this issue, it is necessary to delete two variables from MySQL "nodes". On each MYSQL nodes of you environment, follow these actions below :
1.Connect to PHPMyAdmin with the credentiales sent by e-mail 2.On the dashboard, navigate to Variables tab of your MYSQL nodes 3.Search the vairable sql_mode and delete NO_ZERO_IN_DATE,NO_ZERO_DATE in the value
You can now add posts in Wordpress admin.
To have more information regarding the issue, you can check here : https://de-ch.wordpress.org/plugins/incorrect-datetime-bug-plugin-fix/