Process model referenced to older CDT version in target environment

1. There are chances that either you or someone from your team had that process model open on the source environment when you modified it and the same got deployed to target. (This is probably the case)
2. The PM was open on the target env by either you or your team when you deployed the model and hence it could not get updated. 

To resolve this, check if your PM on the source is referencing the right CDT. If yes, go ahead and ask your team to close all the application objects and then re-initiate the deployment. 

Thanks for your response. So As per above comments we should not keep objects open in source and target environment while deployment, correct?

Yes. Don't keep its dependent objects open in source env. while updating an object. And do not keep the original objects open in the target while deploying. 

Got it, seems like this could be the reason. Anyways, do we have any Appian documentation to be followed while deploying?

Got it, seems like this could be the reason. Anyways, do we have any Appian documentation to be followed while deploying?

docs.appian.com/.../Application_Deployment_Guidelines.html

  once any provided solution works for you or helps you understand what was wrong, please take a moment to accept the answer so this thread can be marked as closed.