Troubleshooting

Images: nothing changes on my pages

Open the plugin’s dashboard and press Check my site. It names the step that fails: no converted file yet, a file the server does not deliver, a wrong content type, or server rules that are ignored.
Clear your page cache once after the first conversion.
With the picture tag method, look at the page source: each image should sit inside a <picture> element. Some page builders print images in ways WordPress filters never see; server rules cover those.

Images: no AVIF files

The dashboard says whether your server can make AVIF itself. If it cannot, AVIF goes through the conversion service: a few images a day without a key, 10,000 a month with one.
When the daily allowance is used up, or a key is refused, the plugin pauses its calls instead of retrying, then carries on later. The log in Tools shows the reason.
AVIF above quality 60 is often bigger than WebP; such files are discarded on purpose. Keep the default of 45.
The status page shows whether the conversion service is up.

Check, in this order: it is published; the page matches Where; your screen matches Screens and Who; today is inside its dates. Then the frequency: once you have seen it, it waits for the next visit or period. Preview on the site ignores all of that and opens it at once. To start over as a visitor, use a private browser window.

A fourth live popup on the free version is saved as a draft rather than published: unpublish another one, or add a key.

Private Space: a members-only page is still visible

You are probably signed in as an administrator or editor, who always have access. Check in a private window.
Purge the page from your cache: it may have been cached before you ticked Members only.
Files in the media library are never protected, by this plugin or any plugin that does not put PHP in front of the uploads folder. Keep confidential documents out of it.

Private Space: the CSV import refuses rows

The preview lists every row it did not understand and why. The usual causes are a missing email column, an address that already has an account, or an address with accented letters, which WordPress cannot store as an email and which is reported rather than silently changed.

Menu Styles: two menus on the page

Expected: the plugin adds a menu where you place it and never replaces the theme’s. Remove the theme’s menu from its location in Appearance → Menus, or from the header template in a block theme, and keep the block.

Beyond five styled menus without a key, the extra ones are not shown to visitors rather than shown broken. An administrator sees a note in their place.

Still stuck

WebP & AVIF Offload has a full system report in Tools and a section in Tools → Site Health → Info. Keep it at hand, then see the contact page.