Getting an error occurred

[inmarpvasadi]

I have used SmartGrid as you mentioned Lookup and Primary Entity for Account and Contact. It worked.

The same way using rest api, I applied with the context of contact as Primary Entity and child as custom entity. I have tried many combinations, still no luck. I believe, Is this control works only standard entities ?

[PowellPowell]

I'm also receiving this error when trying to create a new line: