I've trained over 30 blacksmith and tailors in my years playing UO.
You'll hit dry spells every now and then. I've seen 400-500 hammer swings between gains before. It happens.
Here's a few things to try.
Make something different, something considerably more difficult to make than what you've been making.
Take a break. Stop for an hour or two and come back. Sometimes you get a gain right away.
Commit suicide. Kill yourself. Undress, grab some poison and go to a healer and drink it. However you do it, just do it. Totally and completely unproven but quite commonly recommended when you hit a wall during training.
Last but not least, check your skill cap.