I just launched a new wp-multisite installation and by default we are not installing any plugin in the path where you are having the issue
/opt/bitnami/apps/wordpress/htdocs/wp-content/plugins/WP-API/. As you can see, with the next command we are listing all plugins installed, we don't install anything named WP-API.
ls -lah /opt/bitnami/apps/wordpress/htdocs/wp-content/plugins/
drwxrwxr-x 4 bitnami daemon 4.0K May 17 08:44 akismet
drwxrwxr-x 10 bitnami daemon 4.0K May 17 08:44 all-in-one-seo-pack
drwxrwxr-x 3 bitnami daemon 4.0K May 17 08:44 all-in-one-wp-migration
drwxrwxr-x 6 bitnami daemon 4.0K May 17 08:44 google-analytics-for-wordpress
-rw-rw-r-- 1 bitnami daemon 2.3K May 22 2013 hello.php
-rw-rw-r-- 1 bitnami daemon 28 Jun 5 2014 index.php
drwxrwxr-x 16 bitnami daemon 4.0K May 17 08:44 jetpack
drwxrwxr-x 6 bitnami daemon 4.0K May 17 08:44 simple-tags
drwxrwxr-x 8 bitnami daemon 4.0K May 17 08:44 versionpress
drwxrwxr-x 2 bitnami daemon 4.0K May 17 08:44 wordpress-mu-domain-mapping
drwxrwxr-x 3 bitnami daemon 4.0K May 17 08:44 wp-mail-smtp
Can you try to uninstall/deactivate this plugin? As my coworkers previously said, it seems this plugin is the source of the problem. Can you paste here the output of above command?
About PHPmyAdmin, if you are using a private key to connect to the server, use the following command:
ssh -N -L 8888:127.0.0.1:80 -i KEYFILE bitnami@SERVER-IP
NOTE: If successful, the above commands will create an SSH tunnel but will not display any output on the server console.
While the tunnel is active, you should be able to access the phpMyAdmin console through the secure SSH tunnel you created, by browsing to http://127.0.0.1:8888/phpmyadmin.
To log in, use username root for MySQL and the application password from the detail page for your cloud server.
Carlos R. Hernández