Domain opens a New Setup Page

Greetings

I have a client with a domain name and several sub-domains
each subdomain has the same config file except for the database table_prefix.

This has worked fine, until recently…

Now each time we type in the subdomain The initial Welcome to WordPress form opens up.

I don’t want to fill that in fearing that it will overwrite the site.
It all looks good via FTP and this has been confirmed by my hosting company (1and1)

Any thoughts?

Thanks

Graeme