To assist in resolving your issue, could you please provide some additional information in relation to your installation. As part of your 12c configuration, and with APEX 4.2 installed in your container database, how have you configured your new pluggable database (PDB) i.e. using EPG or APEX Listener or Oracle HTTP Server, as outlined in the 4.2. Installation Guide for 12c
? The reason I ask is because, if you're using EPG, for example, each PDB will have a distinct port number and you'd need to ensure that the URL you're using to access the APEX Administration Services is the correct one.
When you mention that you've installed patch 4.2.2, how did you do this? Currently, it is only feasible to install APEX 4.2.2 complete distribution in a 12c container database by firstly removing the default APEX 4.2.0 installation and then installing the complete 4.2.2 distribution. It is currently not feasible to patch a 4.2.0 instance in a container database with a 4.2.2 patch. The necessary scripts required to carry out such a patch will only be made available in our next patch release. In the meantime, users can still install the 4.2.2 in a container database. To do so, you'll need to ensure that you followed the steps outlined in Jason's blog, here: Application Express Nuggets: Application Express 4.2.2.00.11 for Oracle Database 12c Container Database.
I hope this helps.
I tried follow Jason's blog (exactly as written), but failed again on last step when asking about ADMIN password.
10.Change your container to the PDB that you want to be an Application Express instance and then run apxconf.sql as described here. Use apxconf.sql from the 4.2.2 distribution, not the one in $ORACLE_HOME/apex.
ORA-01435: user does not exist.
alter session set container = pdborcl;
select * from all_users;
do not shown APEX_040200 user