When the bounce rate in any sequence exceeds 25%, it is placed in the Suspended status. This makes it impossible to reactivate this particular sequence. You can only
duplicate the sequence and move contact there.
The issue might be caused by low quality contacts with a lot of outdated or incorrect emails that can hurt your domain reputation and negatively affect your future sequences.
To avoid this, we strongly recommend validating your contacts. You may use our validation service or any other service you prefer before launching your sequences.