M365 & Squarespace issues since defederation from GoDaddy

Since defederation from GoDaddy I can log in to webbrowser version of Outlook, but can't access any apps inc outlook. I get the following error message:

AADSTS50020: User account 'tom@latitudecoaching.co.uk' from identity provider 'https://sts.windows.net/7ad90692-fb43-4b2d-9f3b-81ac4524c15a/' does not exist in tenant 'latitudecoaching.co.uk' and cannot access the application 'd3590ed6-52b3-4102-aeff-aad2292ab01c'(Microsoft Office) in that tenant. The account needs to be added as an external user in the tenant first. Sign out and sign in again with a different Azure Active Directory user account.

I also get error messages from Square Space despite records being refreshed:

SSL certificates are unavailable
These domains are not correctly connected to your Squarespace site. To fix this, use the Squarespace Defaults preset from the dropdown menu in DNS Settings.
latitudecoaching.co.uk
www.latitudecoaching.co.uk

I have checked on Entra and Azure to ensure profile is set up, but I don't appear to have admin rights.

Having discussed with Microsoft I have removed all KeyChain records, cleared Cache and reset laptop but problem persists.

It could be due to conflicting personal and other work accounts, or the fact I originally set up a email under Thomas and switched to Tom.

Anyone that is an expert that can solve the 365 and SquareSpace issues on Monday 22 Jan would be much appreciated.