On a longarm, you don't lower the presser foot so that isn't her problem. I donthave a ton of experience yet, but I set my bobbin case tension first.i use a towa gauge and pretty much know that my magic number is 180 for tension but you can do the drop test and hold the thread in one hand and the bobbin should slowly drop like a spider from a spider web. Then I just use some practice fabric and adjust the top tension till i like what I see stitch wise. I run my fingernail under the backing on the bobbin thread to intermittently check my stitches. Your fingernail should not catch the thread it should move freely on the stitching line with no catches if that makes any sense.