I found a typo in the invitation mail.
You write 'Accept your invitation by visting:' but it should be 'Accept your invitation by visiting:'. You misspelled the word 'visiting', it is missing an 'i'.
You have been invited by <USERNAME> to become a contributor to >USERNAME>/>REPOSITORY> on bitbucket.org.
Accept your invitation by visting:
This invitation will expire in 30 days.
The Bitbucket Team