Thanks for the replies. we did a little more digging and checked the js console, as mentioned in:
And there we did find errors.
What is odd is that we have two instances of LibreNMS, both on CentOS and both at the same version and on the same PHP versions and only one of them has started having this issue. The other one is still working fine.
The ‘validate config’ was showing us that there were missing files under ‘Updates’, so we ran ‘github-remove -d’ which solved our issue.