In the second sentence, the part before the comma is an adverbial, and receiving is a form of non-predicate verb. The ing form and past participle form of some verbs can be used as adjectives (but not in this sentence), such as waiting room, fishing rod and gerund (that is, verb ing) as attributes, indicating the use, purpose or occasion of the modified noun, which is often used in modern English. Gerund as adverbial can only be modified by not, but not by don, because don is an auxiliary verb and can only appear in predicate form, while gerund is non-predicate, so it can only be modified by not.

Note: Non-predicates include gerund, past participle and infinitive.