The reason for this issue is that, missing entry for CUSTOM_TOP under default.env file. In R12, CUSTOM_TOP should be defined under default.env in $INST_TOP/ora/10.1.2/forms/server directory.
After cloning or Autoconfig this issue happend. In Apps R12 undaer $INST_TOP/ora/10.1.2/forms/server/default.env is there. Just add the custom top in that file.
Other wise add the same in XML files permentally.
1. Login apps user
2. cd $INST_TOP/ora/10.1.2/forms/server directory.
3. Cofirm that your CUSTOM_TOP's are registered in the default.env file.
This means that, you should create an entry for environment variable CUSTOM_TOP (which contains physical path to your custom directory) like below in default.env file present under location $INST_TOP/ora/10.1.2/forms/server directory.
Add below entry in XML files, So that automatically this patch registerd to default.env.
4. Not required restart any services
5. Close the login page and again try.