Accept a workspace invite by opening the mail or selecting Join on Home when you see You have invites. Sign in with the invited email so the link matches the address the admin used.
Accept from the email
The accept page is titled "Accept invite". It asks you to sign in with the invited email.
Open the invite email and follow Accept invite.
Sign in, or create an account, with that same email.
Finish join. Home then belongs to that workspace.
If you are already signed in as someone else, switch account before you accept.
Accept from Home
When you have no workspace yet, Home can show "You have invites" and a join action.
Open Home.
If you see "You have invites", join the workspace named there.
If you see "No pending invites", you are on the wrong account or the invite is gone.
"No pending invites" also says "Ask an admin to invite you, or sign in with the invited email."
Invite unavailable
"Invite unavailable" means the link cannot be used. The page says "This invite is expired, already used, or was sent to a different email address." Ask an admin to send a new invite from Settings → Members.