Issue Trying to Embed a Collection in Another Collection

[ColleenRobledoGreeneMLISFTxSGS]

Hello.

I regularly embed Collections into other Collections, and I teach my colleagues how to do that too. But suddenly this week both a colleague and I are receiving an error message when trying to do that (see screenshot). I have tried this out on Chrome, Firefox, and Safari, including clearing cache. I have also tried it on multiple computers, and I keep receiving this error.

Did Esri stop allowing this?

Thanks.

Colleen