Default Closing Account in G/L Options > Account has been set to a valid account? Closing period unlocked in Fiscal Calendar? Retained Earnings account is setup as "Retained Earnings" Account Type?

Yes to all

Any GL error batches sitting open?

Yes, I found three GL error batches not posted yet. Please note that these error batches are not the closing entries. They contain entries posted with fiscal period of 2018 which had caused the error.

To ensure that this is not getting in the way, I posted these three error batches and tried running Create New Year. Still same issue -- no closing entries were generated.

Yes, I found three GL error batches not posted yet. Please note that these error batches are not the closing entries. They contain entries posted with fiscal period of 2018 which had caused the error.

To ensure that this is not getting in the way, I posted these three error batches and tried running Create New Year. Still same issue -- no closing entries were generated.

FWIW, I have Norming Asset Accounting installed but Year End Processing has not been run in the AM module yet. Could this be the reason ?

No. The FA module sends entries to the GL but that is all.