@Dave... No age restrictions, but there are fewer requirements if the trailer is over 25 years old (CAN to USA) or over 16 years old (USA to CAN). Newer vehicles require proof of compliance with respective transportation safety regulations (and emissions, if applicable). With trailers it's mostly about
lighting, maybe
brakes over a certain size. I would start at the Canadian customs website and search on "importing vehicles."
@Carrie... When did you bring the trailer across the border? Did you receive a customs form at the time? Can you still communicate with the seller?
Not sure exactly what DMV is asking for, but CAN vehicles don’t have titles; a
registration document serves as proof of ownership. Not sure if it includes a transfer of ownership section that goes with the buyer or not. That could be what they’re asking for. Perhaps someone from CAN will clarify that...
USA-made trailers after 1981 should have a
VIN, but before then and coming from abroad may not. Look carefully on the tongue; it could be buried under layers of
paint. If nothing and as long as the documents are in agreement (I would want a government-issued document, not a bill-of-sale), then you can stamp it on the tongue yourself. While you're at it, you might add the VIN in another discreet location or two in case of theft.
With lost documentation, a closed border, and limited DMV services in many states, you are in a difficult place. It will take time, patience, persistence, and probably some cost to fix.