Hey there, a name gets changed to a default 'Redacted' when it gets reported, manually reviewed by Bungie, and reset to default due to a code of conduct violation. If you have name change available, you can change it. If you can enter a new name into the name change box, this is proof that you have a name change available. If it's just not saving, then it means the new name is hitting the name filter. If you definitely do not have a name change available, then you would not be able to enter a new name in the box. Additionally it will say 'no name changes available' below it. In this case, you'd have to wait until Bungie issues another name change token to everyone.