I had the same problem where passing multiple arrays for the same key wasn’t working. Instead, just use one array, set ‘value’ to an array of values, and set ‘compare’ to IN:
$args = array(
'meta_query' => array(
'key' => 'key1',
'value' => array('value1', 'value2'),
'compare' => 'IN'
$query = new WP_Query( $args );
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