I started a new job several months ago, it's a hybrid role but the company is very flexible - there are no mandated office days and my manager has said I can do what I like. I like to work from home, so that is what I have been doing. I went into the office once to meet my manager, and then got the chance to meet a couple of colleagues in-person too. But other than that I've been working from home.
Nearly all of my colleagues (including my manager) are based in the 'main' office which is in London, whereas I'm up North in a smaller office - it's mainly for other teams but there are 6 of us in my team/department who are based there. They are very close and lovely, and they added me into their group chat when they heard I'd be based in the same office as them. However, as I have been working from home I haven't been replying to any general messages in the chat (none were directly addressed to me, so I haven't been ignoring them - just when they ask if anyone is going in on X day I don't reply). I also thought there were more people in the chat then there were, so thought it was less obvious if I didn't reply and thought there were several others also not replying, but after checking I realise there's just 5 of us in the chat so I feel rude. They are now organising a social, and it is something I feel really uncomfortable with so I don't want to go. I also missed the last social as I was unwell straight after getting back from annual leave - so also didn't reply to those messages as I was on annual leave and then off sick.
I feel really embarrassed and rude, and they must think it's weird that I don't respond to their messages and that most of them still haven't met me in person. At the same time, they're probably paying me no thought and if I suddenly popped up with a message they may had forgotten I had been in the group.
I know I'm overthinking this, I had a bad experience in a previous job. But how can I sort this situation out?
Thank you