We don't currently have any reported issues with Santander connections, to troubleshoot, I'd be grateful if you could please logout and sign-into QuickBooks via an incognito window on your browser and select the 'update' button.
If this does not resolve, please try disconnecting and reconnecting the feed. To disconnect, go to Banking and select the pencil icon on the bank tile > Edit account info > Tick the box 'disconnect this account on save' and save.
After this, please select 'link account', search for your bank's URL and follow the on-screen flow to re-authorise your bank connection.
Please get back to us below if you're unable to update the account following this. 🙇♀️