A fickle announcement
Add a message, announcement, quote, whatever towards the top of your forum, which is, well, fickle. It will show when someone first enters your forum, but as soon as they click on a post, it goes away and won't come back until a full page refresh is done.
composer require zerosonesfun/flarum-ext-fickle-announcement
composer update zerosonesfun/flarum-ext-fickle-announcement php flarum cache:clear
Also, clear your browser cache and cookies. Also, clear things like your cloudflare cache if you are using a service like that. Basically, clear everything after an upgrade.
Install and activate, go to your forum, maybe refresh the page if needed, then you will see the instructions.