Hi,
Ask someone with Admin privileges to double check your user role still has access to the Mobile app.
https://docs.marketo.com/display/public/DOCS/Grant+Users+Access+to+the+Check-in+App
Hi,
If you are using the same credentials for login in Marketo.com and Marketo event app then go to Admin-> Users & Profiles and check if you still have Mobile Application/Permission role added in your profile. And if you are using different userid for Event App then Go to Admin-> Users & Profiles and check the user's Access Expires date. If the date is a past date then correct it or if the date is valid and then reset the password.
Thanks