Why is "he/his" not accepted here?
"andata" is feminine. That's why. :)
"Lei era andata" correct
"Lui era andata" masculine subject feminine past participle
When "ESSERE" is the auxiliary verb, the past participle must decline according to the subject.
So, "Lui era andata" is wrong, and "Lui era andato" is correct? (Sorry if it should be obvious. :)
Yes, exactly. :)