Agree you don’t want to format it or this could be a really bad day
Is it possible to get some more details like: storage type, storage protocol, etc. Strictly speaking is should be simply a case of presenting the LUN to the new ESXi server and then scanning for new storage.
could u please share more info, Any specific error?type of storage etc.,
I am sure on second host you are starting 'add datastore' wizard.
As ThompsG mentioned. You need to format it once only while adding it on first esxi host. On second and followings hosts you need to make sure you have configured HBAs correctly for ISCSi or FC and rescan adapters for newly presented device lun. This will mount datastore itself.