The "problem" may not be new, but I just discovered that some css classnames are censored by either the browser (Chrome 84.0.4147.105 in my case) or its extensions (Adblock supposedly).
It has recently been the case for a cookie banner with a classname of "c-cookies" : while there was no problem on any other laptops or phones I used to test the website in question, one computer in particular completely ignored the cookie banner, not rendering it at all.
I haven't figured out why this specific laptop had such a behaviour yet (no error visible in the console), but changing the classname from "c-cookies" to "c-cks" corrected the issue.
Two questions for you : is there any documentation regarding "not-to-use" keywords ? And have you already encountered a situation like this ? Google wasn't my friend on this one, no documentation found anywhere (but my phrasing may be bad too).