Is the book using British English? Because in North American and Canadian English, the past participle of "to get" is "gotten". But in most other types of English (e.g. British English), the past participle is "got" instead of "gotten". "Gotten" is only used in phrases such as "ill-gotten gains" instead. Otherwise, the book might be supporting the use of "got" instead of "gotten" as a past participle because the present perfect form, "have gotten", can only be used in some contexts, but not others, making it a little confusing. For example: You can say "I have gotten your letter." and "I've got your letter" But you can only say "I have got to go now or I'll be late." and not "I've gotten to go now or I'll be late." So I think in order to avoid the confusion, most types of English prefer standardise the verb and use "got" as a past participle instead.

I'm not sure there is anything wrong with this sentence. It is another way of saying 'I haven't received any emails for a few days.'. Informally, you can use 'in' with a time period to mean the same as 'for', for example "I haven't seen her in a long time.'0

I agree -- there's nothing wrong with the sentence. You can use "in" instead of "for" with negative sentences, but not with affimative sentences. Example: I've been on italki for a bit over a year. I cannot use "in" in that sentence.

As said Su Ki, I do not think there is anything wrong with that sentence. I would like the phrase I have not received any emails for a few days. Now that I see the other person wrote exactly that. It is just simpler English and sounds better. However, there is nothing wrong with your sentence I have not gotten any emails.

Thank you, Richard.