Unfortunately, Affinity Designer doesn’t have an auto-trace feature, so you’ll need to re-set the text and re-draw things by hand.
If you’ve done that, things ought to import okay. If not, you’re probably just embedding the pixel image in the SVG and then trying to open that in Easel which is what it’s trying to say — that it can’t do anything with an SVG which is nothing but a pixel image.
Another possibility is that AD sets the size to 100% — you may need to open the SVG in a tool such as Inkscape and re-save it to import into Easel.
Post the SVG?