As part of the upgrade process, database objects are deployed and various scripts run against them. This includes the wfdeployclrassemblies stored procedure which deploys the .NET Assemblies required by Workflow for such tasks as AD lookups and sending of emails.
However, I’m going to make the running of this stored procedure a standard, manual, part of the upgrade as I am finding that if it isn’t run after the upgrade is complete, that AD lookups don’t work until it is (this usually manifests in approvals failing to find a user to email or approvals failing if the user had the email from before the upgrade). I might was preempt and do it manually every time in order to give clients a smoother process. To run the stored proc, open SQL Server Management Studio and, against the system database, typically called DYNAMICS run the following (it’ll take a few minutes):
The other issue I’ve now seen more than once (and have also seen when upgrading some clients to prior versions), is that during the upgrade the Workflow managers are lost: