Have you tried connecting via sqlplus using APPS credentials? Are you able to connect?
Is listener running on apps server?
Ps –eaf|grep lsnr
R12 Adstrtal.sh Fails with "Database Connection Could Not Be Established error starting all services on the target" (Doc ID 1499837.1)
R12: "adstrtal.sh: Database connection could not be established" Error When Running Script adstrtal.sh and adstpall.sh (Doc ID 1492611.1)
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