Training and citation are separate doors. Blocking ClaudeBot only opts your content out of training future models; per Anthropic's crawler documentation, it has no effect on whether Claude cites you. Citations ride the other two bots: if you want to appear in Claude's web-search answers, keep Claude-SearchBot (search index) and Claude-User (live fetches) able to reach you, whatever you decide about ClaudeBot.
As with other AI crawlers, the most common reason an Anthropic bot cannot reach a site is an unintended bot-management or firewall rule, not a deliberate robots.txt block.