Please be more specific about the diagnostic and the context of your question. First, under Main Form, there is no #12 although there is Sch E > 12 = Sch E.
It sounds like you may have linked the attachment to Sch E but did not index it to any activity. Suggest you take another look at your entries on the e-file Attachment page.
If that's not the issue, you'd need to come back with more details.
In case your issue is the same as what's discussed in the thread below...
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