Samsung SSD T5 / Only setup partition mounting

Hi, I have been using this drive as a TimeMachine backup for a few months now. Suddenly it has started mounting only the setup partition and the Samsung app refuses the show the main drive, saying that there is no Samsung Portable SSD connected even though it is, as the setup partition is shown on the desktop. I've checked the settings in Security & Privacy and there is no Samsung software that needs permission. HAs anyone else had this problem and if so how did you overcome it. There seems to be no way to re initialise the drive as only the setup partition shows in Disk Utility and that shows as a read only partition?