Hi @Elizabeth Higman ,
Do you mean that you can't find the site you are following from the place shown in the screenshoot below under https://<tenantname>.sharepoint.com/_layouts/15/sharepoint.aspx?
If so, you can have a try to clear cache and cookies of your browser or change a browser to see if it fixes. After that, if the site still doesn't appear under "Following", you may wait for up to 24 hours as some timer jobs in the backend have to be executed.
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