Yeah I just checked Atkinson Hyperlegible and, at least the version I can access (the one on Github) lacks entire Latin and compatible character ranges, as well as having a substantially limited math symbols set (only two greek letters show, for example).
The weird thing is, if I understand how fonts correctly, that shouldn't have been an issue. The font doesn't register those missing characters, so your browser should have known to fallback to a default typeface for the missing characters. It'd be weird if you have none of the many compatible fonts (not even, say, Times New Roman).