Can the assistants read your site at all?
Check robots.txt for blocks on OAI-SearchBot, Claude-SearchBot and PerplexityBot. These are the live-search crawlers, and blocking them removes you from consideration entirely.
This is the first thing to check because it's binary and it's common. A site that blocks the live-search crawlers cannot be cited, no matter how good it is. The blocks are almost never deliberate — they arrive with a security plugin, a CDN bot-protection default, or a robots.txt copied from a template written when 'AI crawler' meant something else.
Worth separating clearly: the training crawlers (GPTBot and similar) are a genuine privacy decision and reasonable people block them. The live-search crawlers are the ones that fetch a page in order to answer a question being asked right now. Blocking those costs you the citation and buys you nothing.