I recently took some studio portraits using eye detection with auto eye selection. I didn't have one failure. There is either something wrong with the camera or lens, or more likely, an incorrect setting. Check all the relevant settings and test. Are you sure you didn't accidentally move the focus lever to manual? It's easily done. Or you might have left one of the special focus modes (animals etc) selected.
Hi, just wanted to also share this has been an ongoing problem with my Voigtlander lenses as well (27mm f/2 Ultron, 35mm f/.9 Nokton, and 50mm f/1.2), ever since the last firmware update for the X-T5. Anyone know if this bug is being addressed by Fuji?