ReadyNAS 316 invited ReadyCloud users cannot access shares

Yes, all the account names (= email addresses) consist of 32 or less characters. I'm haven't seen any possibility of creating account names that aren't the email addresses.

And yes, I deleted the accounts and tried to reinvite them several times. If one clicks at the invitation it appears to be accepted (or at least not declined from the appearing message window) but the users continue to appear pending in the user list and the users cannot see the shares.