Domain or subscription gets suspended automatically every day despite the fact the red question mark next to the subscription does not show any exceeded limits/resources:
Entries like the following can be found in Plesk Action Log in Tools & Settings > Action Log:
127.0.0.1 admin [2017-09-21 17:08:30] 'Update Domain Status' ('Domain Name': 'example.com' => 'example.com', 'Status': '0' => '2'
The following can be found in Plesk > Subscriptions > example.com > Account > Resources :
Alternatively, if the affected subscription is owned by a Reseller, the following can be found in Plesk > Resellers > Log in as Reseller > My resources and permissions overview:
Subscription or Domain overuses the resources available or expiration date has passed.
To find out why exactly domain is suspended, going to Plesk > Tools & Settings > Action Log and click on Download. In the downloaded action log file, search for the domain name that was suspended.
Both Expiration Date and Resources can be managed globally via Service Plans > Default Domain > Resources or per-subscription basis via Subscriptions > example.com > Customize > Resources.
Note: In case per-subscription solution is used, the subscription will become locked for sync with the Service Plan.