This error message can be difficult to diagnose. The error message is saying that Importacular can not find something it was expecting to find. It is not a very useful error message because it does not specify what Importacular was expecting to find.
It is also difficult to diagnose because we can not ascertain if the issue is because of a change in the Raiser's Edge, in the data source or a change in the Importacular template.
As such, it is incredibly difficult for support to replicate the issue.
To help diagnose the issue, please look to any changes made to your Raiser's Edge configuration: tables, fields, Campaigns/Funds/Appeals, attributes, etc.
Also look to the data source. Are there any fields that are now missing?
Finally, look to the template in Importacular. Are there mappings that are now blank? Are there Data Transformations that point to a particular field/value that are no longer populated?
If your research does not resolve the issue, you may wish to consider copying your template and then start removing mappings one at a time, re-running your import to establish where the issue is originating. This process of elimination is time consuming, but has a higher chance of discovering and resolving the issue.
Alternatively, you may wish to start a new template from scratch.