Thanks everyone for the comments.

My stats hadn't worked for the entire 10 days but it seems I pasted the wrong bit of code in my sites. Something to do with Standard Analytics and GA4 analytics.
Google Support suggested I stick with the standard option. And I was shown how to delete the existing properties so I can recreate them later.
I further complicated my own setup because unknowingly, I had previously used one of the domains in a different google account already. So I have shut down that old account.

Google Support are willing to help you set up your analytics (or fix them as in my case) for free, if you have a google adwords account.

Thanks again for the advice and comments.

I don’t have much experience but I am wondering if somehow you are mistaken. It doesn’t make sense that this just happened because it seems like things were functioning.

Hi Max,

I think it will take a good week until it gathers your site's data. Based on my own personal experience, I had to wait a good one week or may be even 10 days until there were some data gathered in it.

To me it looks you did everything right and only 3 days are not enough. I think you should allow it some more time until it collects data.

I hope it helps,

Meena

I had the same issue and contacted site support to change the gtags so they were the same as the added one for me and it didn't match the ID I had on my account.