ReadyCLOUD "Invite new user error" [RESOLVED]

Hi Everyone!
I'm having issues trying to configure ReadyCLOUD access with my RN316.

I have a ReadyCLOUD account set up for User A. When I try to link the RN316 to ReadyCLOUD using User A credentials, I keep getting an error that the user account exists and I need to remove the User or Cloud user account. LAN User 1 had the same email assigned as User A. However, User A is not listed as a cloud user or LAN User. This error continued even after I deleted the email address from User 1 settings.

I then created another ReadyCLOUD account for a new user using a different email address (User B). I manager to get the RN316 to register on ReadyCLOUD using User B credentials. I then proceeded to add users via ReadyCLOUD website. User C was added without any problems and shows up on the RN316 admin GUI as a cloud user. I get the following error message when I try to add User A:

Invite new user error
4280450001
Failed executing sys operation on device

From the error messages it seems like there is something wrong with the CLOUD user listing on the NAS. Please advise how I should proceed to sort this out.
Thanks, Shaun