Different fabric, different tension
I bought 6 batik fabrics to use in a wall hanging from a quilt shop, so nice quality fabric. I had the project about half done when my new sewing machine started skipping stitches and then eventually not catching the bobbin thread to stitch a seam at all. I rethreaded the machine with both the spool and bobbin, changed the needle, cleaned my machine, used different thread, changed the pressure on the presser foot, etc. When I would sew on a piece of scrap it would sew fine and I would think I had it fixed until I started sewing on my project. Then I got wise and used a piece of the batik for a scrap and sure enough it wouldn't sew. Turns out it was the fabric all along and when I started having problems with it skipping some I was using the one batik with another. When I used two layers of the problem batik is when I started having problems of it not sewing at all. I adjusted the tension and got it to sew again. The other five batik fabrics from this same purchase sew just fine with the automatic tension setting on my machine.
I've solved my problem but I'm posting this in case others have had a similar experience or in the future may be sewing and start having stitch problems. It may be the fabric and not the machine. In all my years of sewing I've never had something like this happen. I've had to adjust settings for different types of fabric but never when the only apparent difference in fabrics was the color.