EIC Qualifying Child Non Dependent Credit

I'm a little confused by the whole EIC Non-Dependent Credit.

 

Person A is a disabled adult child who works and remains under SGA. Draws SSDI also. Person A files taxes this year and claims himself so he can get his stimulus. Personal A lives with Person B all year. He selects under My Info they can't be claimed. On their EIC form, it gives an option they can check that they were disabled and can be claimed by Person B. Person A doesn't qualify for EIC then. Person A goes to review taxes at the end, and it says Form 8862 needs reviewed and line 4 must be blank.

 

Person B is the mother of Person A. Person B is not claiming Person A as a dependent but can qualify for EIC on Person A for being disabled and living with them all year.

 

Why would the first person get that link 4 must be blank situation?

 

Can Person A claim themself and not qualify for the EIC and Person B(the parent) qualify for EIC on Person A in this situation as a non-dependent?

 

Can't a person be a qualifying child to the parent if they're totally disabled and not claimed as dependent? I thought that is what the non-dependent EIC was for.