"Underlying keyring service returned an error" whilst trying to set up encrption (no replies)

Hi I am trying to set up encryption for the first time with MySQL 5.7.18 for the first time.

I am following the tutorial but have hit this brickwall when trying to generate a key using: SELECT keyring_key_generate('MyKey', 'AES', 32);

Error Code: 3188. Function 'keyring_key_generate' failed because underlying keyring service returned an error. Please check if a keyring plugin is installed and that provided arguments are valid for the keyring you are using.

Both keyring plugins are enabled and active:

show plugins...

# Name, Status, Type, Library, License
'keyring_file', 'ACTIVE', 'KEYRING', 'keyring_file.so', 'GPL'
'keyring_udf', 'ACTIVE', 'DAEMON', 'keyring_udf.so', 'GPL'

I created the functions without error:

CREATE FUNCTION keyring_key_generate RETURNS INTEGER SONAME 'keyring_udf.so';
CREATE FUNCTION keyring_key_fetch RETURNS STRING SONAME 'keyring_udf.so';
CREATE FUNCTION keyring_key_length_fetch RETURNS INTEGER SONAME 'keyring_udf.so';
CREATE FUNCTION keyring_key_type_fetch RETURNS STRING SONAME 'keyring_udf.so';
CREATE FUNCTION keyring_key_store RETURNS INTEGER SONAME 'keyring_udf.so';
CREATE FUNCTION keyring_key_remove RETURNS INTEGER SONAME 'keyring_udf.so';

I have disabled selinux and have pointed "keyring_file_data" in my.cnf to a directory with all permissions.

Any suggestions appreciated.

Thanks