Symptoms

I am editing an existing report. I am changing a from clause. I can query and get a result back. When the query window is closed, an error appears stating that it cannot refresh the fields. I cannot build the report thereafter. The error reads "Must declare scalar variable "@ProcessID""
 

Diagnoses

The issue was related to the Parameter name not being @ProcessID, but just ProcessID. The Parameter value is @ProcessID however, and this out of sync name and value causes the issue.
 

Resolution

The issue was resolved by changing the parameter name from ProcessID to @ProcessID.