There are several reasons I may not respond.
1. I may not think or realize it required a reply (for most feedback, suggestions, etc.).
2. It may have ended up in the spam box and was cleared before I got to check on it (I only check my mail a few times a month or when I receive a new message notification, which doesn’t show when it goes in the spam box).
3. It’s appears to be or is obviously spam (advertising, nonsense, etc.). Those will never receive responses.
4. It never reached me at all. I have filters in place that doesn’t let some things get through.
5. It’s for offers I do not need or care for.
6. Address domain is fairly known for fraud, isn’t legit or spamming.
If your contact was legit, I apologize. Right now certain domains are not even looked at and/or are auto-deleted and for good reasons. The only option in those cases is contacting through another source that’s more reputable. Also lately I only check my mail for this site maybe 1-2 times a month, so it might be a bit before I get to it anyways ^^;;