Does this only happen with a couple of people or everyone? It seems like a parameter isn't passing correctly.
Are you using the full link in the URL or are you using the Process Approver link configuration as described in the Design.pdf file?
1. On the Settings menu, click System.
2. Within the Process Approver settings, alongside the Enter the Web Access Process
Approver URL property, type:
http://<Server>/<WebAccess>/object/open.rails?class_name={Class/Module/Name}.{Class/Name}&key={Guid}
Then in your auto reminder within your workflow add this in somewhere:
In addition to the message, you must add the following to the Details box, so that the user can click
it to authorise the relevant process.
<a href="{$ApplicationSetting.ProcessApprover.WebAccessApproverURL$}">Click Here</a>
This will actually mask the full link in the email with "Click Here". It'll pass the full link through tto your Integrated or Explicit framework depending on what you use.
Hope this helps somewhat.