The fabric I am sewing is very soft and therefore the stitch does not hold onto the material, works fine with cotton etc. What do I need to do to so the stitch is showing. Manual didn't help. Thanks

Machine settings usually need to be re-adjusted when the project materials change, ie the needle size & type, the type/weight of thread, the presser foot pressure, the thread tension, the stitch length, etc. Sewing woven cotton is very different from sewing silk or chiffon. Test on scraps of the fabric before actually sewing on the garment. Even adding tissue paper to the stitching will help prevent fabric puckering.

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Try setting the stitch length to a longer stitch. Increasing the stitch length should move the material faster. Also, make sure that the presser foot pressure is not to heavy. This shows up sometimes when you change fabric thicknesses (denim vs lightweight sheer) and the machine has difficulty moving the fabric. Try stitching on different fabric and see if it makes a difference. Also, if the material you are stitching is somewhat sticky, it will stick to the bottom of the presser foot (this is common when sewing vinyl, leather, etc.) If that is the case, you may want to check into getting a leather roller foot (it has wheels built into the presser foot that will turn as the fabric is pulled through by the feed dogs).

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make sure that the thread tensions are correct for the thickness of material
remember that only the bottom foot walks and draws the material through so it may need a help and be pulled as it sews.
I find that women in sewing shops just love to talk about problems and how they can help so find a shop and discuss any problems with them

You need a ball point size 70 or a jersey 70 if you can get it. Stitch length 2.3 to 2.5. Re tension, just normal tension setting. If the machine is sewing an evenly balanced zigzag on regular cotton fabric, then tension is fine. If you find the straight stitch on your fabric pops under stretch, then try using a very small zigzag to put some flexability into the seam.

Try a ball point needle which is for stretch fabrics. Using the wrong needle can cause skipped stitches.

if the machine still sews a straight stitch on top of fabric & also on bottom then it should be fine..
it's possible that the thick fabric, needle, & thread were not a compatable combination.
but also some sewing machine are not made to sew thick or heavy
fabric
but having the machine serviced would be a good idea & help to know why the needle thread is not working

Check the bobbin tension too. It could be too tight. Make sure you are using the right size needle for the material as well. Sheer, thin fabric needs a smaller needle, thicker material requires bigger needles. Bobbin tension is the typical problem as most think to adjust the top tension but don't check the bobbin tension.

Is your quilt peices cotton? Cotton shouldn't cause as much trouble sewing along the edge but don't use too long of a stitch length else it will seem to gather up. Puckering side to side however is a tension problem usually. With sheerer fabrics that cause a problem sometimes you can put thin paper underneath, sew through both and then pull the paper off after sewing. (thin like the iron on type interfacing type fabric but like paper).

With any stitch problem, always a good idea to re-thread the machine - top and bobbin also - making sure the threads go into their correct tension areas. The next best stand-by "cure-all" is to replace the needle. Use one appropriate to the project being sewn. There are different size needles for finer through to heavy materials, and different needle types for lingerie fabric, regular cotton, denim, stretch etc.

Be sure to have the right needle for the right material! that sounds maybe a bit like I am taking you for a ride! but not! I sew professionally and have a box full of needles! Most of the needles you buy in the shop have a designation (jeans, jersey etc! ) afterwards there is something like 70, 80, 90 up till 100!
70 - very fine fabrics, silks and sheers
80 - fine fabrics, thin cottons
90 - average and 'normal' fabrics
100 and more - thick fabrics, curtains etc!
If your problem persist, you may need to take your machine for servicing! how old is it? and what brand? yours,
rick

Try a different needle, matched to the weight of your fabric.