ORA-65086: cannot open/close the pluggable database

SQL>
SQL> SHOW PARAMETER pdb;

NAME TYPE VALUE

autotask_max_active_pdbs integer 2
awr_pdb_autoflush_enabled boolean FALSE
awr_pdb_max_parallel_slaves integer 10
disable_pdb_feature big integer 0
enable_automatic_maintenance_pdb boolean TRUE
enabled_PDBs_on_standby string *
max_datapump_jobs_per_pdb string 100
max_pdbs integer 254
one_step_plugin_for_pdb_with_tde boolean FALSE
pdb_file_name_convert string
pdb_lockdown string

NAME TYPE VALUE

pdb_os_credential string
pdb_template string
scheduler_follow_pdbtz boolean FALSE
standby_pdb_source_file_dblink string
standby_pdb_source_file_directory string
target_pdbs integer 9

SQL> shutdown immediate;