HI im having the same problem, debug says this:
Thanks
[05-Dec-2019 18:22:35 UTC] WP Offload SES #101: Mail function already overridden.
[05-Dec-2019 18:23:36 UTC] WP Offload SES #101: Mail function already overridden.
[05-Dec-2019 18:23:38 UTC] WP Offload SES #101: Mail function already overridden.
[05-Dec-2019 18:24:01 UTC] WP Offload SES #101: Mail function already overridden.
[05-Dec-2019 18:24:01 UTC] WP Offload SES #101: Mail function already overridden.
[05-Dec-2019 18:25:36 UTC] WP Offload SES #101: Mail function already overridden.
[05-Dec-2019 18:25:37 UTC] WP Offload SES #101: Mail function already overridden.
[05-Dec-2019 18:26:01 UTC] WP Offload SES #101: Mail function already overridden.
[05-Dec-2019 18:26:02 UTC] WP Offload SES #101: Mail function already overridden.
[05-Dec-2019 18:26:10 UTC] WP Offload SES #101: Mail function already overridden.