Shella

Hello, unfortunately after the upgrade to 2.12 on my Fujifilm XT-4 I cannot connect the camera to the APP. I believed was some problem with the phone (Andorid Oneplus 9 Pro) but I tried to pair even with an iPhone and another Android but nothing. Pair is not working. Any idea how to solve? I heard that there is a very tricky way to downgrade but seem too risky to me. Thanks in advance for help