Site restored to sub-folder shows blank page

I have copied all the root files and the following folders:
– includes
– misc
– modules
– themes
– sites
– profiles

to the sub folder.

I have edited settings.php to point to a new database and I have restored a copy of the original database into the new db. The restore worked without error.

However when run the url to the subfolder I see an empty page – page source:

<html>
   <head></head>
   <body></body>
</html>

I know I have done something silly as I have used this sub-folder restore procedure successfully in the past. But I just can’t work out what. Normally when this fails there is some sort of error or obvious site restore failure that points to the problem. Never have I had just a blank page ! Thanks.

Drupal version: 


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