Carey B. okay got it - the fact that it failed that quickly tells me that its being blocked from the host. The import URL uses crawlers. So in the SiteGround hosting settings, if you add relume.io or relume.ai to an allowed list of crawlers, and try again it'll work. Or temporarily disable blocking of crawlers/bots.
Not much we can do on our end.
This was tested using AI and in its tests it also reached a 403 Forbidden block, which confirms the above.
