Use of personal pronouns to reference inanimate objects

Hi Paul, I need help on a grammar question. In lesson 10.4, Koffer is referenced in one sentence by "er". This seemed logical to me since Koffer is masculine. However, two phrases later the reference is "es". This seemed wrong, but when I brought it to the attention of support, they assured me that the reference in this instance should be genderless. I'm afraid I don't understand why "er" is correct in one sentence and "es" is correct in the other. It seems inconsistent. See phrases below from lesson.10.4 thanks, Byron Matthias: Ich glaube ich habe meinen Koffer verloren. Ich warte schon seit einer Stunde an dem Fließband, aber er ist nicht da. Sandra: Wie sieht Ihr Koffer aus? Können Sie ihn beschreiben? Matthias: Ja, natürlich. Es ist ein großer schwarzer Koffer mit kleinen Rädern.

Hey,your better than me in German.I've got no idea.

I was never satisfied with the answer I got on that. Most of the lessons use the same pronoun as the gender of the object whether or not it is inanimate. Another example is where Jäcke (Jacket, feminine) is referenced by the feminine pronoun sie. I was never able to get an answer that I could understand to explain why Koffer was referenced with a masculine pronoun is one sentence and with a neuter pronoun in another. I thought the neuter reference was an error because Koffer is masculine, but support insisted it was correct. After a few exchanges, I gave up.

I'm with you. Makes no sense to me, but the more deeply I get into the course, it seems the German language, at times, is something that just doesn't always follow what we would deem as "the rules."