@pokilo Its "die Instanz", Instance isn't a german word. As loanword it would be "die" too.
As a rule of thumb, nouns derived from latin in german mostly have the same gender as the original ones. In the case of computer the gender comes from the -er suffix, which like the french -eur demands a male gender :)
@material_boy ok, in French is "la" so feminine to but we also have the word instance in French and it's feminine but you say Der Computer and we also say un ordinateur in French, so I think it doesn't really make sense