apex version? db version? listener version?
is this on your machine or apex.oracle.com?
what options did you use to create the workspace?
You might have created a schema also. what options did you use to create the schema?
This sounds like you've reached your Quota for the tablespace.
You can free up some room by deleting some data
Or, you can contact your DBA to increase your Quota limit for the 'offending' tablespace.
Can you check your schema's space usage from Administration > Monitor Activity > Report Tablespace Utilization (popup)
Tablespace Name Bytes Amount Used Amount Free Percentage Used FLOW_15952 16,777,216 14,417,920 2,359,296 85.94
If the Free space is low, you may request for more space from Administration > Manage Service > Make a Service Request > Request Storage.