Error while creating relationship (direct query)

Hello all,

Good day!
I am trying to use direct query in the pbi. My datasource is coming from 2 pbi datasets in the cloud.
The SAP table is from a dataset
Both of the Cheat Sheet table comes from another dataset

I trying to create relationship between this table, the 'Cheat Sheet (clean)' to 'SAP' =blue line, it is successfull. But when I tried to do the same with 'Cheat Sheet (not clean)' to 'SAP' =red line it throw the error in the pop-up.

Please let me know what this mean, and how to workaround this?

Thanks