This occurs when Office 365 has encountered an internal error and is an error with Microsoft's services.
We recommend turning off the Microsoft Threat Protection facility where possible.
You can also log into the app without using the email. Just enter your email address into the app as before, but then click the 'Having issues? Press here' link. If you click "I cannot access this email account" you will be able to login using your email address and password.
Alternatively, check out the following FAQ's on other ways to log into the app/access your tickets:
You can also head directly to www.skiddle.com/orders to access your ticket(s) at any time.