Gitlap pages: custom domain doesn't reflect update. Common causes?

Hi, I’m a developer with relatively limited experience of setting up DNS records etc. I’m using gitlab not self-hosted.

I pointed a google domain to my gitlab page, it worked, but then a push didn’t show up, though it does show up on I’ve googled, read the docs and the wiki.

The DNS record looks like this:

I’ve obviously done something wrong. Any help gratefully received.

Still haven’t found a solution to this. I’ve re-read the docs and stroked my beard some more without result.