I have loaded a NIEM 2.1 IEPD  file into ConTesA and received the following error message: An IEPD or MPD must contain at least one exchange schema artifact that defines one and only one root element for instances specified by the IEPD or MPD. Have you have any toher users with this message and what was done to resolve it?

In 2.1, EVERY schema that is NIEM-conformant MUST declare itself such with an i:ConformantIndicator.
Otherwise, the ConTesA ignores the schema and will NOT apply any conformance rules
because it does not recognize the schema as NIEM-conformant.  
Here is an example for an exchange schema that should be immediately below the Schema element:
<xsd:annotation>
                <xsd:documentation>exchange schema</xsd:documentation>
                <xsd:appinfo>
                                <i:ConformantIndicator>true</i:ConformantIndicator>
                </xsd:appinfo>
</xsd:annotation>
This should also be applied to conformant extension schemas as well.
User should see the subset schemas – each one contains such an annotation.
Note that once these have been inserted, ConTesA will apply other conformance
Rules tailored to the schemas to determine what they are (reference, extension, exchange).
There will likely be other auto rule failures at that point that had not appeared earlier
because no rules are applied to schemas that are assumed to be non-conforming
(because they do not declare conformance with i:ConformantIndicator = TRUE).
(a few namespace import issues will likely appear – these will need to be fixed as well)