Any sewing experts around? Sewing machine can't cope with my lovely fabric!

[FFSN]

I am attempting to upholster an armchair and have bought some lovely velveteen fabric to cover it with. I did a practice cover using some cheap as chips fabric first, all went well. But now I've started with the proper fabric, the sewing machine has gone bonkers! It either goes through the motions but no stitches actually happen, or it does really silly mega long stitches that are less than useless. I am a relative sewing machine novice so just don't know what the problem could be. Can anyone advise what I need to check/do to make it work with this fabric??

You may need different needles.

https://inspiredtosew.com/blogs/sewing-essentials-getting-started/how-to-sew-thick-or-slippery-fabric#:~:text=Use%20a%20longer%20stitch.,a%20small%20zig%2Dzag%20stitch.

First of all, are you using a new needle and the right size needle

Next - is the fabric slipping as you sew? You need a lot of pins and probably a walking foot

Is your tension set correctly? Even an automatic tension machine may need adjusting for thicker layers

For a heavy weight upholstery fabric id guess you’ll need a 90/14 or 100/16 needle, and to set the stitch length a little longer to allow for the thicker seam.
If it’s a stretch velvet look for a ballpoint or stretch needle.

Thanks for suggestions. Allthough its veveteen its not that thick...but it is slippery. Not using a new needle...I'll try that.

Thanks for the link @flowerchild2000 , looks good!

Once you’ve sorted the needle size and the tension, you could also try cutting tissue paper into strips and pin it over the seam allowance, it helps with the slipping around.