Mailbox Created in O365 Admin Page Not Showing On Premise

Hi,

So all of our current O365 users have been migrated from on premise mailbox's. Although we have had a few hiccups this has gone overall relatively smoothly. We are running in a hybrid environment and our dirsync is currently working fine.

Last week I created a mailbox through the admin page in the O365 portal. The mailbox has created fine and logged in to login.microsoftonline.com I am able to send and receive e-mail. However unlike with the migrated users, outlook 2013 does not automatically find the mailbox. I have looked and I can't find an on premise object in our Exchange Admin Center, which I assume is the reason for this. In the EAC when I click on the Office 365 link in the top left corner and log in I can see all of our O365 user mailbox's and this user shows in there.

When I try to change the reply address on this mailbox I get the following error:

The operation on mailbox "" failed because it's out of the current user's write scope. The action 'Set-Mailbox', 'EmailAddresses', can't be performed on the object '' because the object is being synchronized from your on-premises organization. This action should be performed on the object in your on-premises organization.

This seems pretty self explanatory in that it is still synchronizing, however I have had this message since the mailbox was created which suggests to me that something is wrong.

I would just delete his mailbox and create a new Office 365 mailbox in the on premise EAC however when I select his mailbox in the O365 Admin portal I can Add to Group, Edit and Reset Password, but delete is not clickable (I have checked with another and it is). I assume this is just due to the state that the mailbox is currently in but I still suspect there is a problem.

I assume there may be a way to connect with powershell and delete his mailbox, or some logs or other information to check somewhere that I may not know of. I am relatively new to the Administration side of this.

Thanks,