I would say the database user did not have space privileges on the tablespace.
drop and create the user from a sql prompt then "Grant unlimited tablespace to <user>" as dba. then associate the repository
(associate should do all the creates and inserts)
(Granting "resource" used to give space privileges on the tablespace, not in 12c.)
You can create a table in the tablespace with no data in 12c as that is a metadata operation - no blocks are touched in the target tablespace.
An 'empty' starting repository has a few data entries such as its version number.
Thanks! That was the issue. I was using documentation from OTN. Made the suggestion to update that to include this: "Grant unlimited tablespace to <user>" as dba since it looks like it is unique to 12c. Thanks again.