Warning Notification – Internal Malfunction

I had to manually install with Plesk and the only page of my website that shows up is the Home Page. To view any page of my site I have to set it as the front page from the reading settings. This is my third attempt to seek help on this issue.

I get ‘Warning: Compilation failed’ on the “plug-ins” and “other word press news” menus on the dashboard.

It appears to all be from one error:
‘Warning: Compilation failed: characters with values > 255 are not yet supported in classes at offset 31 in /var/www/vhosts/leachandwalker.com/httpdocs/wp-includes/class-simplepie.php on line 11043’

I opened the file and on line 11043:

function is_isegment_nz_nc($string)
{
return (bool) preg_match(‘/^([A-Za-z0-9\-._~\x{A0}-\x{D7FF}\x{F900}-\x{FDCF}\x{FDF0}-\x{FFEF}\x{10000}-\x{1FFFD}\x{20000}-\x{2FFFD}\x{30000}-\x{3FFFD}\x{40000}-\x{4FFFD}\x{50000}-\x{5FFFD}\x{60000}-\x{6FFFD}\x{70000}-\x{7FFFD}\x{80000}-\x{8FFFD}\x{90000}-\x{9FFFD}\x{A0000}-\x{AFFFD}\x{B0000}-\x{BFFFD}\x{C0000}-\x{CFFFD}\x{D0000}-\x{DFFFD}\x{E1000}-\x{EFFFD}!$&\'()*+,;=@]|(%[0-9ABCDEF]{2}))+$/u’, $string);
}

I assume it’s some kind of server setting beacuse I think this local ISP is new to WordPress hosting and their tech guy doesn’t really know. But my clients’ site has been down for some time so any guidance is greatly appreciated.