Older Metal Tubes - How can I get them to work?

I recently aquired my grandmother's old set of Cameo Silhouette Designer Paint Pens (In metal tubes with rubber pump button on top).

I can feel that there is still paint in most of them but none of them will work. I tried soaking. I the tips in warm water, no luck. I pumped and rolled them trying to clean the tips, but again no luck.

Does anyone have any tips?

Thanks in advance!