Sorry for jumping into this thread
I am working on a website and its users faced a similar issue (screenshot attached, Mobile Chrome browser)
I haven’t personally faced this, hence I found this odd.
It is likely not a propagation issue for this website as it has been on Cloudflare for over two weeks
I also went through Community Tip - Fixing NET::ERR_CERT_AUTHORITY_INVALID, but the quick fixes recommended there, didn’t help. Reading through them, I got curious about the 8th fix. Could you be able to share more details about the timing issue mentioned in the 8th fix?