If you have the new newest version of PHP you may want to isntall isntead from the following zip.
backup-brooklyslcadmin
If there is some null deprecated error try replacing with:
protected static function formatPrefix($new, $old, $prependExistingPrefix = true)
{
$old = $old['prefix'] ?? null;
if ($old !== null) {
$old = trim($old, '/');
}
if ($prependExistingPrefix) {
return isset($new['prefix']) ? $old.'/'.trim($new['prefix'], '/') : $old;
} else {
return isset($new['prefix']) ? trim($new['prefix'], '/').'/'.$old : $old;
}
}