Per EA on Twitter: “Update
Players who upgraded Monster Maker players should have access Ultimate Team again.
Players can safely upgrade Monster Makers going forward.
We have disabled chemistry options on Monster Makers for the time being as we are investigating an issue.”
https://twitter.com/maddennfldirect/status/1580743669136920576?s=46&t=ziMZWyvsuvNdH4pmf39bIg