Work and school accounts belong to your organization, and its IT admin can stop apps like Newton from connecting. If a Microsoft 365 or Google Workspace account won't connect, check these causes in order.
Try these, in order
Use the right sign-in. For Microsoft 365, including Exchange Online, choose Microsoft 365 or Outlook on desktop, or Outlook in the mobile app. For Google Workspace, choose Google on desktop or Gmail in the mobile app.
Look at what the sign-in page says. If your organization hasn't approved Newton, Microsoft's or Google's sign-in page stops you before you can allow access and shows its own message. When you leave that page, Newton reports Microsoft sign-in was cancelled. (or Google sign-in was cancelled.). You see the same message if you close the sign-in yourself, so it doesn't tell you which happened. On desktop it appears in your browser under We couldn't verify your account. In the mobile app, the browser just closes and no account is added.
Ask your IT admin to allow Newton. Admins can approve Newton for you or for everyone in the organization. Tell them which permissions Newton asks for (listed under Good to know).
Check where your mailbox lives. If your organization runs its own Exchange server instead of Microsoft 365, Microsoft sign-in can't reach your mail. Ask your admin whether IMAP is turned on. If it is, add the account with IMAP using the server settings they give you.
Try again once Newton is approved. Add the account again. On desktop, Try again on the browser page restarts the sign-in.
Good to know
Newton asks Microsoft (Microsoft Graph) for Mail.ReadWrite, Mail.Send, MailboxSettings.ReadWrite, User.Read and offline_access.
Newton asks Google for full Gmail access (https://mail.google.com/), gmail.modify, gmail.readonly and gmail.settings.basic, plus your basic profile and email address. It asks for calendar access only if you turn on the calendar in the desktop app.
If Newton says Microsoft sign-in failed followed by a code in brackets, send that code to your admin. It's Microsoft's reason for stopping the sign-in.
Newton can't get around your organization's rules. Only your admin can change them.