Cannot create a public link !

I've placed several PDF files in the same folder and sent out public links to them.  Normally using "   Send Link" from either the corner (▼) menu of the document in the folder view, or the Share menu of the specific file's view, will in fact make it public the first time it is invoked, and give me the link to copy.  I see a recent change to the dialog box added some other option switches, so the problems might have to do with the recent changes.

For a few days I've had a problem where I use the "   Send Link" menu item to get the link again, and it states that it's private (which is wrong) and doesn't provide a way to change the status in that dialog, which is not normal; this happens after the page has been in the browser for some time, and reloading the page fixed it.

But now, I have a new file that I cannot share at all.  I've tried reloading the page.  I've tried logging out and back in.  I've tried to find another way to change the status (the Access property under the Details view for the document) and still it only complains that it's not public, and does not make it public nor provide any way to change that.  Existing (already public) items behave properly, as described in the first paragraph.

Please help.