Resubmitted after fixing Guideline 2.1, still Waiting for Review

Another developer here, not Apple, so I can't see the queue. But you can confirm the two things that matter yourself:

1. The resubmission carries the new build. The version page's Build section should show the new build number. Over the API: GET /v1/appStoreVersions/{versionId}/build. Worth reading back even if you are sure you attached it; the attach call (PATCH .../relationships/build) answers 204 whether or not it took.
2. The submission is queued. GET /v1/reviewSubmissions/{submissionId}?fields[reviewSubmissions]=state should read WAITING_FOR_REVIEW, and the version's appStoreState the same. After a rejection, the resubmission reuses the rejected submission's id, so seeing the old id there is expected. If a second, empty submission shows up under Draft Submissions, that is a stray container from an earlier attempt; remove it there.

If both read that way, nothing else is needed from your side; the next state is IN_REVIEW.

One more thing to check while you wait: which inbox review mail actually goes to (Users and Access → your user → Notifications, plus the Account Holder's address). On one of our apps the verdict went to a mailbox nobody read, and we saw REJECTED in the API four days before anyone saw the email.

Free scripts for the read-back checks, MIT: https://github.com/vskromny/appstore-release-kit

Good Luck! Im still waiting since 12 September…! App ID: 6747684577