Confused to Tow

I have a Nissan Quest MiniVan, rated 3500#. I went to a dealer today, and they basically told me that I would not be able to tow a Trail Manor, not even the 2619, that basically all I would be able to tow would be a pop up. I am new to trailering, so I am a bit confused what I can really tow.

In simple terms, does anyone have any suggestions for what to look for in a trailer weight that I can tow with my Quest?

Also, does anybody have any experiences of towing Trail Manor trailers, possibly the 2619, or 2720, with vehicles rated at 3500# such as mini vans?

We really like the design of the Trail Manor Trailers better than the Pop Up Trailers, but if we really shouldn't tow them with our Quest, then we will have to begin searching other options.

Thanks for any ideas or help.