iPhone app won’t record in 4K

I have an iPhone 15 with 1TB storage. For my Blackmagic app I have set it to record in 4K. However it sems to only record in HD. It is set for HEVC, but I have tried Prores as well, but the recordings are all HD, even though the camera app says 4K.
However can I get the app to record 4K?
Thanks.
However can I get the app to record 4K?
Thanks.