In the past, there have been reports of Let's Encrypt's OCSP servers being blocked in China.
The current OCSP servers are on a different domain name than they were at the time of those reports, and I haven't seen any such reports within the last couple years. Of course, they could start blocking it at any time if they wanted to, and anyone on this forum might not know of it happening.
I think some people do. Some people have found it difficult to get the traffic allowed for the validation attempts from Let's Encrypt's servers.
Of course, some people in other countries (including the US) have trouble getting their ISP's firewalls to cooperate too. 