This question has been answered by sottwell. See the first response.
Firstly try going to /setup ( presuming you never deleted the setup folder ) and see if it asks you to install or upgrade., if it asks you to upgrade go ahead and do that to see if that solves it, if it asks you to setup it means that it's not connecting/detecting the database so make sure that the connection details in core / config / config.inc.php are correct and the database is actually ok
Firstly try going to /setup ( presuming you never deleted the setup folder ) and see if it asks you to install or upgrade., if it asks you to upgrade go ahead and do that to see if that solves it, if it asks you to setup it means that it's not connecting/detecting the database so make sure that the connection details in core / config / config.inc.php are correct and the database is actually ok
Is the message in a large red bar, or is it a standard web server error message?
I had this situation once before years ago. The hosting provider had moved the domain to a different server without notifying their customers, so the paths were no longer valid.
I had this situation once before years ago. The hosting provider had moved the domain to a different server without notifying their customers, so the paths were no longer valid.