Depending on several variables, reviewers may not see the correct form if the form is missing certain properties.
Make sure when assigning a Reviewer, that the proper Review Stage was selected during the process. If it was, then navigate to your Blueprint module and make sure the Review Form they should be seeing has the appropriate "Assigned Group" or "Assigned User" associated with it. Assigned Users are users accessing your Blackbaud Grantmaking database. Assigned Groups could be groups within your Organization, or in the case of an External Reviewer, be associated with the "Reviewer Portal System Group".