Some wallets and exchanges seem to incorrectly give the error that our addresses are not valid, which is not true, they are definitely valid.
We use multi-sig DASH wallet addresses that start with a "7" while regular DASH addresses start with an "X". These two address types can send to each other just fine and neither of them are invalid, it is an issue with your wallet/exchange's address validator. You will have to route your transaction through a wallet that does not have this problem.
This is a non-exhaustive list of tested wallet providers that support the multi-sig address format:
If you find any other wallets/exchanges from which you can deposit DASH to Celsius, please shoot us an email at firstname.lastname@example.org and let us know!