It means the receiving wallet is not fully synched for any one of a variety of reasons including a possible bad address.
The receiving wallet needs to run the -rescan option or update to the newest client or maybe just even restart the wallet.
~BCX~
Hi, Thanks.
Forgive me I am a total novice at this and this is my first foray into cryptocurrency so a lot of this goes over my head....but I'm learning

(hopefully).
I have shut the wallet down several times and reopened but no change. Is that what you meant by 'restart the wallet'
As mentioned i'm on a mac and can't see a rescan option anywhere, options a very limited.
I get a feeling that i'm on a back foot anyway being on a mac with this and should wait for the PC wallet to sync.
back to the question I asked about addresses, if you create multiple wallet across different platforms will they all have different address of they can have a common address?