Ruben has a Mac that he runs Windows in boot camp. He has an NTFS drive that he needs to read from time to time. When he reboots back into macOS Catalina, the hard drive partition isn't recognized and won't mount. Leo says it sounds like macOS has messed up the partition used to run boot camp. He recommends backing up the data, repartitioning the drive and then reinstalling Catalina. Look up FUSE drivers: it enables you to read/write NTFS drives in macOS.