Upgrade via admin panel fails

try ing to upgrade to c1.5.10 from v1.5.8 via the admin panel.
Get the error message
'Grav update failed The target path "C:/laragon/www/atex" does not appear to be a Grav instance' where 'atex' is the site folder.

I am running laragon wamp (Apache2) on a local windows 10 PC as a test server. There was no problem upgrading the remote production version.
See www.laragon.org for more info
The site as it stands works perfectly on the test server.

Any ideas what causes this error?
Thanks

Looks like I've solved the problem.
Somewhere down the line the local copy of the bin folder was deleted.
Replacing it from a downloaded copy seemed to do the trick.

I would have expected a 'file not found' or similar error message, would have made fault finding easier.