Escalation rules is not working

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Hi All,

I am not using SLA in Escalation.

I have specified 2 level of escalation. As per rule first level escalation is working fine.

For Next level escalation - I have created one custom field to capture the incident last updated time.

By using the custom field, I have specified 2nd level escalation 

For example:

1st level:(working)

if -Status equals open

Then- Escalate to level  10 mins

         +30 mins from (Date created)

2nd level: (not working)

if -Status equals open

Then- Escalate to level  20 mins

         +20 mins from Custom Field (Date last updated)

Any idea will be helpful

Thanks,

Seethalakshmi