Same problem on our 27HFS. The filler opening and neck were both level or actually below the tank opening.
Mobile RV repair company lowered the tank with 2 pieces of 2" steel tubing. Filler neck is now angled downward, but I'm not convinced it will take fuel because the fill port is still sitting at a 90' angle at best.
If the fix did not work, I'm going to have to resort to a "beer funnel" type setup to get fuel into the tank.
Funny.....the $5,000 generator can't operate because of a cheap filler port. This RV thing will always be far from perfect.