When it came to wishing Prince Harry a happy 40th birthday via social media in September, King Charles III was “happy” to send the message. However, His Majesty is reportedly still harboring trust issues with his youngest son thanks to his Sussex 75th birthday phone call last November, of which details were “leaked” to the media. “One thing I did find out is how really disappointed the king was back in November when Harry did call him to wish him not just a happy 75th birthday, but also his children did a little video singing happy birthday to the grandpa they barely even see,” royal expert Re…