The subscription is suspended for no reason after Daily Maintenance task is completed.
How to check what limits have been exceeded by subscription?
Set up a corresponding email notification in Tools & Settings > Notifications : check Resource usage limits exceeded by subscription and Subscription suspended due to resource overuse event for that.
Once the limit is exceeded, the email will be send on the corresponding mailbox, e.g:
The following resources were overused by subscription 'example.com', owned by user 'John Doe':
Sites published with Presence Builder: 01 used / 0
The subscription was suspended.