site not displaying in iphone “reader view”

I think the problem is the client device and not your website. I have an iphone xr and an iphone 10 and can view the site in both. I’d suggest regular browser maintenance to the client device to fix the problem for it.

For your own independence, here is a great blog post explaining how you can view different device screens via chrome’s dev tools. The directions work very similar in Firefox. I did look in Firefox for you as well though.