HCM Communicate - Get Responses Campaign no button shown in email

Summary:

we are testing email for a Get Response campaign that has 2 buttons (one for YES and one for NO).

After performing the Send Test campaign, the email arrived into the inbox has 2 different behaviors:

1° behavior: No buttons shown (email server Outlookweb app)

2° behavior: buttons shown (email server Outlook 365)

The Response Choices are configured using both the options: external link and Thank you page.

Why the button are not shown in some cases?

Version (include the version you are using, if applicable):

24A