Unable to merge HDR for TIFF file

Hello Lr community, following my last question, I foudn that the problem with HDR Merge not working is because of file format, if i have three TIFF files they will not merge but if I use Raw it will, this happened only recently because I did use TIFF on LrC before and they still work on Lr and Ps, is this because of settings or updating? I tried reinstall LrC but it doesnt work. I am using Tiff instead of Raw is because ACR doesnt recover as much detail as the camera manufacturer's software and it only outputs tiff