Failure to start warm migration

I am attempting to use a policy to transition indices to UltraWarm storage. However, each time the migration to UltraWarm begins, Kibana displays the error, "Failed to start warm migration" for the managed index. The complete error message is below. How can I find more details on the root cause of this issue / a fix for it. Thank you!

{
"cause": "\[753f6f14e4f92c962243aec39d5a7c31]\[10.212.32.199:9300]\[indices:admin/ultrawarm/migration/warm]",
"message": "Failed to start warm migration"
}

Edited by: JaredvH on Jul 21, 2020 3:05 PM