I recently moved a Craft 2 install from a server running PHP 5.x to one running PHP 7.x. All seems to be well. The custom "system offline" message appears as expected when visiting the home page, anyway. It also appears when visiting a random URL.
But when visiting the admin URL I'm redirected to the installer. I'd obviously rather not do this as the system and DB are already there.
Do I have any options here?