I orginally restored my site on my hosts Apache server using the cPanel backup but I cannot get my site to load without giving an error

Did the usual uploaded the zipped file which unpacked and restored perfectly, but when I go to the web address of my site it keeps coming up with an error.

I also cannot log-in to the admin, have I missed out an important point is there something I haven't done.

I have not changed the database (this has also been backed up).

Any help would be most helpful

Thanks

Mark