Google rejecting lack of IPv6 PTR while using IPv4

Hi,

So this week my customers have started complaining about rejections from Google with the below complaint.
550-5.7.1 this message does not meet IPv6 sending guidelines regarding PTR
550-5.7.1 records and authentication. Please review
550-5.7.1 https://support.google.com/mail/?p=i...tication_error for more
550 5.7.1 information. h65si9409667ioi.167 - gsmtp

I haven't made any changes and I'm using IPv4. Has there been a change/update in interworx that I'm missing? It was working perfectly last week. This week, emails are getting dropped in spam or all out rejected with the above.

Thoughts?

Thanks!