Event triggered process chain not getting triggered in APO

Dear experts,

There was a system  outage after which one of our process chain is not getting triggered by the corresponding BI event.

Before outage , the process chain in APO was triggered by an event which was triggered by the completion of a process chain in BI.

In BI side the process chain generating the event is getting completed successfully and generating the event but the process chain in APO is not getting triggered.

We have maintained the correct event , parameter in the start variant in the APO process chain and the chain was activated and scheduled after the outage and also the connection between APO & BI are working fine.

Please help if any one of you have come across such an issue.

Thanks

Geethika