Connection problem, local file %s not found

After working fine for ages, this message suddenly appeared:

Local file '%s' not found.
Cannot login waiting to retry (30s)...

I have removed smartFTP, then reinstalled it, same problem.

Apologies if this has been raised before, I did search but couldn't find any reference to it......

What file is %s and what do I do to correct the problem, please.

Thank you so much......will download from this link.

Not sure why this happened, I don't remember any upgrade taking place.......one minute it was working, then for no reason this appeared.