i don't see in what you posted where you granted ABCD\svcaccount permissions in msdb to the procedure sp_start_job; you might have glossed over it, but did you do something like this?
USE msdb;
CREATE USER [ABCD\svcaccount] FOR LOGIN [ABCD\svcaccount];
GRANT EXECUTE ON sp_start_job TO [ABCD\svcaccount];
Lowell
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