Unable to open Workbench. "clase no válida"

Hello. 

I've not used the program for a while in my laptop (I own 2 Freelance Plus 2017 licenses) and now I cannot open Workbench (Multiterm seems to work fine). I get a message that sais: "clase no válida". 

Any ideas on how to solve this?

Thanks in advance.

Regards.

María Marta

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