Fatal error: Call to undefined function

Dear user group
I disabled the excel plugin then I uploaded the plugin again.But now im getting a error when I try to logon to my multi site admin site. Im not sure if its related. Please also review picture attached. Please advise Thanks you .
Jerry

Site: https://solucionesretail.net/wp-admin/network/
Error: Fatal error: Call to undefined function wp_get_current_user() in /home/solucio9/public_html/wp-includes/capabilities.php

on line 522
function current_user_can( $capability ) {
$current_user = wp_get_current_user();

if ( empty( $current_user ) )
return false;

$args = array_slice( func_get_args(), 1 );
$args = array_merge( array( $capability ), $args );