Negative-ない-Form (ADJECTIVE/NOUN/VERB) + こと(は/も)ない as “it’s not that not X” (softened affirmation)
The grammar pattern Negative-ない-Form (ADJECTIVE/NOUN/VERB) + こと(は/も)ない is used with all three of the main types of words (ADJECTIVE, NOUN, VERB) to invoke a double negative effect that softens one’s affirmation of something, while having a final translation that somewhat differs depending on which of the three types of words is being used.
When this construction is used with VERB words, natural translations include “can VERB,” “not impossible to VERB,” “it’s not that [subject] doesn’t VERB,” etc. Of these, it should be apparent that “it’s not that [subject] doesn’t VERB,” is the closest to the literal translation, due to the inclusion of the double-negatives in the grammatical construction itself (“not,” “doesn’t”).
When this construction is used with ADJECTIVE and NOUN words, the common translation is also the literal interpretation of “it’s not that not (ADJ/NOUN).”
Overall, the main intention behind using this grammar pattern as opposed to simply foregoing the double negative construction and going with a single, positive statement is that it adds the nuance of softening one’s affirmation of something. For example, Xが好きじゃないこと(は/も)もない (“it’s not that I don’t like X”) is a softened version of the straightforward Xが好きだ (“I like X”). In keeping this main point in mind, one should be able to correctly interpret this grammar pattern despite the fact that it may end up with a different final translation depending on what kind of word it is used with and the context of the sentence in which it is used in.
Yasai wa tabenai koto wa nai ga, suki jyanainda.
(“It’s not that I don’t eat vegetables, I just don’t like them very much.”)
Anime ga suki jyanai koto mo nai ga, ima wa yoku minai.
(“It’s not that I don’t like anime, I just don’t currently keep up with it as much.”)
Kuruma o unten dekinai koto wa nai ga, taitei jitensha o tsukau.
(“It’s not that I can’t drive, I just tend to use my bicycle more.”)
Sono you na kurushimi o keiken shita koto ga arimasu kara, anata no kimochi ga wakaranai koto wa arimasen.
(“I’ve gone through a similar hardship before myself, so I understand how you feel.”)