Thetford Casette frame sealant

The sealant between has failed between the Thetford casette frame and van body letting rain water into the bathroom soaking the toilet floor, its running in through a crack in the sealant running down and into the case that the casette slides into and out at the bottom of the toilet where it meets the floor. Anyone know what sealant I should use to reseal the frame to the van body to make it water tight.

Thanks

Use non setting mastic on a roll , available from most good caravan spare shops or eBay

Thank you. I’ll get some