SSD Drive Bug

Hi! For some reason everytime I save a project to my attached SSD then shut off the mpc, it no longer detects it when I turn it back on. This has happened two days in a row now with the ssd magically reappearing the next morning. Is this a known bug or is there anything I can do to fix this? I've already ordered an external hard drive but would like it if my ssd just worked.

More information would help, e.g make and model of ssd , capacity, how did you format it and what format did you use (exFat etc)