starting with ONTAP 9.12.1 DP\TDP snapmirror engine is deprecated
 
https://kb.netapp.com/onprem/ontap/hardware/What_is_the_ONTAP_version_requirement_of_TDP_snapmirror%3F
 
Note: Beginning with ONTAP 9.12.1, transisition data protection (TDP) relationships  are no longer supported  for 7-mode volumes.  Use CIFS or NAS tools i.e., (Robocopy, Xcopy, XCP, Rsync, or NDMPcopy) to transfer data to CDOT Clusters then use SnapMirror technology