A quick introduction from my side, my name is Derryn Zwart and I am the product manager of ATS.
I am sorry to hear that! The last couple of days Mendix had issues with their online services due to a cyber attack. Everything that uses the Mendix Online Services was impacted. ATS uses the Mendix SSO and Teamserver API’s to handle the login and permissions and was therefore also impacted. See the Mendix statuspage for more information: https://status.mendix.com/.
Could you let me know if you can login again? Most issues were resolved yesterday. If not we need to investigate.
Apologies for any inconvenience!