ora-28426: must FINISH a tablespace encrypt, decrypt or rekey command first

I have a tablespace test with 4 datafiles, test1, test2, test3 and test4.

I attempted to encrypt  test1 but failed stating the command was not completed, it recognized there are 4 datafiles. Only 1 was encrypted.

alter tablespace test encryption online encrypt file_name_convert ('test1.dbf', 'test1_encrypt.dbf');

I then attemped to encrypt test2 and got ORA-28426 error.

Was there a command to encrypt all 4 datafiles at once?   Alert log advised to reissue the alter tablespace command with FINISH  option.  I am not aware of this command.   How do I encrypt the other 3 datafiles?

Please advise.