Plesk does not allow to activate suspended subscription in Plesk 10.0:
Error: Some of the selected subscriptions were not activated.
Error: The subscription is still suspended due to the following reason: The subscription is suspended.
This error appears in Plesk 10.0 when trying to activate subscription in "Suspended" status, which was automatically suspended due to disk space or traffic usage limit.
This error was discovered in Plesk 10.0.1 and should be fixed in future updates.
As workaround, subscription can be enabled with command line tool
On Linux server:
# /usr/local/psa/bin/domain --webspace-on <subscription-name>
On Windows server:
"%plesk_cli%\\domain" --webspace-on <subscription-name>