It's the first time we are trying to run an event.
I see the administrator has configured an event portal (on 10/10/2019) - our primary domain is almas-industries.microsoftcrmportals.com/
We've created the test event, but when we click on the URL it's giving this error.

Then I decided to check the other marketing pages and we are now getting a similar error on all of them - these were working fine last month.