I filled up a smaller sized Vac this morning. It filled fine. Now I can't get it to write. I can shake it and ink will drop on the paper but, it will not write. Can't seem to get ink down the nib. What do I do?

My experience with Vacs is limited, so I can only suggest what I might do in the same situation. It sounds like there's some kind of block in the feed, while the passage for the breather tube is still free. So, get a glass that's tall enough to support the pen, put enough 1:10 ammonia-water in it to just cover the point (not even the section, at this stage), and leave it soak for a while. Hopefully, this will dissolve whatever is under the point, and get you back writing. If it doesn't, it's probably time for ultrasonics or trips to talented repair-folk.