By the following steps you can easily fix Outlook says disconnected:

Ensure, you're connected to the internet.
Re-input your login details in Outlook as a possible quick fix.
If your mailbox is overflowing, try archiving or deleting older content.
In case you're connected via a VPN or proxy, disconnect it to check if that's the issue.
Exit the Outlook application and then launch it again.
As a last resort, restart your device to resolve any lingering issues.

https://www.emailtechnicalsupport.us/blog/outlook-disconnected/