Reference check for business account

Me and my partner are trying to rent a property and we are dealing with Openrent for reference check in this case. We were asked to provide a guarantor as well even when we both have passed the reference check for renting the property. Now the problem is our guarantor has a business account and they can’t accept him as our guarantor due to this reason. They want our guarantor to have all his savings come out of a personal account. Not sure what the problem is here and we both are really perplexed even after we both have passed all the reference checks.