I haven't tried it either, but many big name sites use certificate pinning to avoid the attacking form of this MITM.
A manually trusted cert overrides pinning, it's only protecting against certs signed by another of the default installed certs (otherwise Google and others simply wouldn't work in many corporate environments).
There might be a better article if you search deeper than I did to come up with a quick link, but here:
https://blog.heckel.xyz/2013/07/01/how-to-use-mitmproxy-to-r...