I hope this is the correct place to post this question. Please feel free to move if not.

Booked YUL-EWR-CPT/JNB-EWR-YUL in Oct/Nov in PY on 014 stock.

When looking to see the cost of purchasing an upgrade to J on the TATL legs on the UA website it indicates no upgrades available, even though EF shows the flights as J9. In fact, outbound is O3 so PY is almost full.

Would this have anything to do with the ticket being on AC stock? Any suggestions to inquire about the cost of upgrading? Any ideas if this would also affect the purchase of an upgrade at check in?

Thanks in advance