Admin invitations should redirect to /admin/signin
When admins accept invitations, they are redirected to the end-user sign-in on the web portal.
In some cases, admins aren't able to sign-in with SSO while end users can.
If the account has the site restricted to SSO authentication, the admins won't be able to authenticate accept the invitation
Braelynn Annalise commented
Site users can create accounts on only one forum (https://www.machinesrating.com/how-to-get-st-augustine-grass-to-grow-back/). If a user clicks on the link to create an account, they will be redirected to a page that says, "You do not have permission to view this site." since they have not been invited. If there is a link, it should lead to a form that is configured with a 'REQUEST ACCESS' workflow.
Emilia Ryan commented
The site has only one forum, where users can create accounts (https://neosabers.com/collections/dueling-lightsabers). Users who click on the link to create an account are redirected to a page that reads, "You do not have permission to view this site." since they have not yet been invited. There should be no link or it should lead to a form configured with a "REQUEST ACCESS" workflow.