It's a known bug of the system when you're relying on bonus TP to get you over the line, it's affected a few people in the thread here - https://www.flyertalk.com/forum/brit...4-edition.html

Give the Gold Line a call (During the day to get someone from the UK) and explain the situation, my OH was affected in a similar way with bonus TP spanning a year, a complaint was raised with the back office team and a few days later it was reinstated.

On the plus side, when they do reinstate it, because you've dropped to silver the computer will likely give you the extra year for going up a tier so there's every chance it'll renew to December 2025.