I canceled my cheaper refundable fare a week ago. Refund for the cheaper fare came back into TravelBank today (1 week later) but I am still out the difference from the original refundable fare.

I don't think a refund for the difference will happen without contacting them as changing the ticket produced new ticket numbers and I believe United sees the refund as complete under the newer ticket numbers.

I checked the refund status using the original ticket numbers and the refund was processed a week later from the change. Called United Refunds and everything was processed correctly so I'll wait out the 20 business days to see if it eventually credits back to TravelBank. It's odd no email came from United Refunds when the fare difference refund was processed yet I got an email today from United Refunds for the cheaper cancelled reservation and funds were immediately back in TravelBank.