SharePoint Designer cannot display the item

I deployed a custom workflow as a farm solution and started getting this error when I try to access the workflow with my SharePoint Designer.

ULS shows no associated info and I cleared out the cache from my local machine on these locations:

C:\Users\myacct\AppData\Local\Microsoft\WebsiteCache
C:\Users\myacct\AppData\Roaming\Microsoft\Web Server Extensions\Cache
C:\Users\myacct\AppData\Roaming\Microsoft\SharePoint Designer\ProxyAssemblyCache