CRiS is a central Register, a bit like DVLA but without the legal compulsion. The key benefit is that it makes it difficult for someone who has stolen a caravan to sell it on to an unsuspecting victim. It may be for this reason that an insurer may decide only to insure 'vans which are on the CRiS database. Indeed, CRiS's website does say "Many insurance companies require CRiS registration before processing a claim". I am not aware which companies have this requirement, as DustyDog says the CAMC policy has no such requirement.
As DustyDog says, 'vans manufactured before 1992 are not automatically registered on CRiS, after this date new 'vans were registered on CRiS in the name of the first owner by the dealer. When a 'van is subsequently sold on, whether this is via a private sale or via a dealer, the existing registered keeper notifies CRiS and the registration will be changed to the new owner/keeper. There is nothing to stop a pre 1992 'van being registered onto CRiS.
I suppose the key issues are:
- whether your 'van is pre or post 1992. If the latter, it should have been registered on CRiS.
- has your insurer made it a requirement that the 'van be CRiS registered. If they have, this should have been made clear to you. Even when insurance quotes are obtained over the telephone, the details are normally confirmed in writing. Under the FCA rules insurers have to ensure that for "consumer products" (ie those sold to the general public) any unusual conditions or exceptions are brought to the attention of the policyholder. There shouldn't be any nasty surprises hidden in the small print.