I’ve posted a few times about errors in Workflow requiring the wfDeployCLRAssemblies stored procedure to be run again (1 2 3), but the Dynamics GP Support and Services Blog has posted an article about how this is sometimes not sufficient to resolve the problem and the procedures, functions and assemblies deployed by the wfDeployCLRAssemblies stored procedure need to be deleted.
To this end, the blog post contains a series of scripts which need to be run before thew wfDeployCLRAssemblies stored procedure is executed. There are versions of the script for Microsoft Dynamics 2013 R2, 2015 (including 2015 R2) and 2016 (including 2016 R2).
If your problem still isn’t fixed, then a support case would need to be raised.