You need to select "Arduino Mini" not "Arduino Pro or Pro Mini" from the boards menu. The naming is confusing, I know. If you still have problems, try varying the timing of resetting the board vs. pressing upload.
You need to select "Arduino Mini" not "Arduino Pro or Pro Mini" from the boards menu. The naming is confusing, I know. If you still have problems, try varying the timing of resetting the board vs. pressing upload.