Harry is obviously grateful for everyone’s support. He couldn’t have possibly made this clearer in every single interview he’s given and he has gone out of his way to actively defend his primarily young and female fanbase from judgement and derision of obnoxious male ~real music fans~ who try to handwave girls’ interest in Harry as being less worthy than their own.
Consider your expectations as a fan. Needing him to tweet “thank you” again and again, turns what’s supposed to be your genuine enthusiastic support, freely given, into transactional “I don’t feel validated in response to this specific self-appointed fan-victory, so I’m upset”.
Harry is allowed to be lowkey on social media. He’s not a machine you put support coins in until acknowledgement tweets falls out.