Why do I keep getting a 'No faces filled' error when using the Face-fill tool? I'm new to Blender (yes, I'm working on a donut) and I'm trying to get my head around the Face-fill command.

I cleaned up an SVG of a logo and imported it to Blender, then converted it to a mesh. Now I'd like to create faces from the logo so I can extrude it and use Boolean tools to essentially 'cut' the logo into a shape. No problem with the part of the logo which was originally just a vector shape drawn in Illustrator and passed to Inkscape. The part of the logo which started as text is a total nightmare, though. I was trying to do it with the F (create face) command and it was creating faces without leaving holes (as in letters like 'b' and 'a'). 

Reading around in the Blender 2.82 manual I discovered the Face-fill command. I even created a shape similar to what the manual shows (by adding a single vertex then extruding it numerous times and setting Snap to Vertex, thereby creating the required continuous perimeter). It just gives me the same (sorry, useless) error 'No faces filled'. Does anyone have any idea how to go about filling more complex vector shapes made up of many vertices?
I ran into a similar issue but was mixing up the &quot;Make Edge/Face&quot; (F key) command, and &quot;Fill&quot; (Alt F keys), &quot;Make Edge/Face&quot; was working