Thanks for responding. I think I did both of the steps you suggest. I did click on both "Free Object" and also "background not on a page"
within the Preflight Verifier and nothing was identified--inside that window.
To be sure I have the terminology correct: Page is the window I created first of all using x-,y- coordinates and started out blank (white), Background is the first "Shape" I created and Shift-clicked to fill with a background color entirely, Image Frame contains the inserted an TIFF photo imported from my desk top and filled to "fit frame size" (visually it might have gotten outside the page coordinates, but was nudged back inside). The Text Frames all reside well inside the colored background and I can't see how they might not be on a Page.
"Objects" are the background color and image text frames that float on top of the Page; there are no Layers I'm aware of unless I have inadvertently done so by inserting the (opaque) Frames on top of the (opaque) background color, underneath.
Since the "Free Object" had the sub-listing as "Background...." beneath it, I clicked that line in the Preflight Verifier and examined the x-, y- coordinates, which match the same as the original Page exactly. The preflight error messages hadn't changed.
I thought maybe there was an "Object" I created that might be invisible? I noted your use of the term Canvas, which in this context I haven't found a Scribus definition for, and assumed it meant the, entire, colored "Shape" that fills the, entire, Page that all the other frames sit on top of (in the same Layer).
But with the notion that Objects might be invisible and floating around like space junk, Canvas might really be a term for all the white space with rulers along the top and left side that contains the Page. I expanded the ruled white space to the limits of my computer screen and to the far right side a colored vertical bar appeared without a frame, just color. I clicked on it this bar and hit the delete key and the colored bar disappeared.
Immediately I returned to Preflight Verifier and, immediately, zipped thru with flying colors, no problem. The only explanation I have for the colored bar is that I changed the background color for another one.
Like exasperating knots that have a simple solution, might I suggest that us neophytes be made aware that Canvases are not Pages and rather worrying excessively over the Page they should cast their nets far and wide in search of space junk.
Thanks, without your mention of the word canvas I would still be starring at my Page, infinity fiddling with it.