Time Machine - Backup Disk Not Available

[adrianwi]

I'd switched across to using SMB for Time Machine last year, and in the main, it has been working OK. No better, or worse than when using AFP so I switched all my network shares across to SMB, even though I'm in a predominantly Apple household.

I'd deleted one of the Time Machine backups as I was running low on space, but after building a new machine I don't have this problem anymore so thought I'd add it back in. The options and permissions on the dataset are identical to the other machines (I have a dataset for each machine backup) and the SMB share settings are exactly the same, but whatever I try and do once I select the disk and enter the user/password I eventually get the notification to say "Backup Disk Not Available. Try backing up again when 'freenas0.local" is available."

I can access the share using Finder and can add new files and folder, so it's accessible and writable from the machine I'm trying to backup.

Any ideas what to try next?

Thanks