'Confirm Subscription' leads to 404 if sign up on mobile

Opt-in for automated welcome email works perfectly if sign up comes from desktop, but Confirm your subscription from no-reply@squarespace.com upon signing up to clients opt-in leads to 404 page when you click 'confirm subscription'. This obviously inhibits potential subscribers (from mobile) to sign up to mailing list.

Client website: https://www.rachelharville.com/

Any genius wholeheartedly appreciated!!!

i have this too, you didnt get any replies - did you work out the issue?