Loose stitches. Have been trying to solve this problem for 3 hours. Needed to replace bobbin

Question

Have been trying to solve this problem for 3 hours. Needed to replace bobbin (empty). Upon rethreading the machine cannot get the proper tension. Bobbin thread comes thru fabric while needle thread lays flat on surface. I have rethreaded multiple times, changed to all the tension settings to  find no change in the stitches. Wasted a lot of thread and don't know what else to do. Help. Thanks a lot.