I receive the same message when I also try to do so.
I already had an operational client previously downloaded, which worked as of 29 Sep 2018, but when I attempted to open it this morning, I received the following message:
"An unexpected error has occurred: One of more errors occurred. (The system cannot find the file specified)
Please go to the Contact page at askmrrobot.com and submit a technical support request if this error persists."
I had hoped to download a new, working client but receive the same message the OP does when I try to do so.
Same here, the client tried to download an update and it didn’t work. When I went to the site to download the new client directly i got the same error message.