I have followed the instructions to display remote content in Thunderbird but some emails still require me to go to their websites to see content. What now?

What "instructions" are you referring to?

Can you describe how these certain emails "require" you to go to their web sites? Do they show a placeholder?

What kinds of remote content are you expecting to see?

There's only one setting in Thunderbird that controls that, <Settings | Privacy & Security | Mail Content | Allow remote content in messages>. There is also an "Exceptions" area there where you can Allow or Block certain sites. How is yours set?

Are you aware of the security implications of automatically allowing remote content?

https://support.mozilla.org/en-US/kb/remote-content-in-messages

I am expecting to see images in my email. My Thunderbird is set to "allow remote content" and I have listed the websites where the remote content does not load as "Allow" exceptions. The emails that do not display the images do quickly flash the images on the screen and then go to a blank placeholder. Yes, I am aware of the security implications of allowing remote content.

Does this happen with all messages with remote images, or just some? If just some, are they all from the same source?

Inline images are only visible in HTML formatted messages. Are you sure they are not just simple text messages? And if HTML, are you confident that they are formatted with valid HTML?

You have three choices of viewing format, "Original HTML", "Simple HTML", and "Plain Text" (see menu the menu options in <View | View Message Body As>.) Only "Original HTML will display inline images. Which view are you using?

Try restarting Thunderbird in Troubleshoot Mode (see <Help | Troubleshoot Mode>.) Do things display more like you expect?

What antivirus or other network security or VPN software do you use, if any? If so, try temporarily disabling it or creating an exception for Thunderbird in it.