Where are you looking?
Mine showed up on my Flying Club account a good while before I received an email about it. I'd even used mine before Virgin Money managed to email me back in February!
However, It does not show on my Virgin Red app for me.
The agent is wrong when they say it only show's up on your card anniversary. It should automatically hit your Flying Club account within 30 days of you reaching the spend threshold.
I actually track my VS card monthly card spend using a spreadsheet to see exactly when I reach the voucher threshold. It's about time VM added this feature to their app. The voucher appeared on my FC account the following month at the same time my monthly spend points appeared on my FC account. The email informing me was received around 2 weeks after that!
Here's my FC transaction:
05 February 2024 5 February 2024 Virgin Atlantic Credit Card Reward Voucher Virgin Points 0 Tier Points 0
My card anniversary is next month (April) as VM recent emailed exactly 1 month before my April statement date to remind me.