Just unplug and replug until the Android file manager shows up. Sometimes it takes a few times or more. Make sure you are using the cable that came with your phone.
Also, when transferring files, it may crash if the files are too big. In that case you need to open the file you are transferring and do it piecemeal. It is a good idea to check each large file that has been transferred to be sure it's all there.
I know this is a pain, but it can be done. Persistence is the key.
Good luck.
Yea, heavy and a bottle of bread.