My texts aren't being delivered to one specific person, but I can get their texts. Any help?

[kt415]

I am having the same problem and have done all the things asked battery taken out deleted contact had them delete me restarted ohone

[Tidbits]

Do you both have iphones? Sending to people who used to have iphones? If the switched away from iphones then they need to dissociate their phone number from iMessages.