Unable to sign up for roles using the agenda embedded in an email

Hello,
The week of July 6th or so our members were no longer able to use the sign up button in an agenda embedded in an email to sign up for a role in an upcoming meeting. Prior to July 6th or so when a member used the mail icon at the top right of an agenda, sent an email with an embedded agenda to members, members could simply click the sign up button and the website agenda would automatically update and add the member to the role. Now the embedded agenda is non-functional for some members or opens another window where the member is asked for user name and password before the website agenda is update. For at least one member the embedded agenda works the same as it did in June.

We did recently update some text on our home page but I am unaware of any members changing any email settings. 

Thank you for your support,
Patricia Ambroziak
Professional Women Toastmasters Club 5077319