1. The ex-husband may feel embarrassed or don't know how to respond: divorce is a sensitive topic for everyone, and some people may not know how to respond, or feel embarrassed and uncomfortable.
2. Ex-husbands may not want to celebrate the first anniversary of divorce: divorce is a painful experience for everyone, and some people may not want to recall the past or celebrate this day.
3. Ex-husbands may have other thoughts or intentions: some people may try to rebuild their relationship after divorce, or have other purposes and intentions, so they may not be willing to celebrate the first anniversary of divorce.
In either case, you can respect your ex-husband's feelings and don't have to force them. If you want to keep a good relationship with your ex-husband, you can try to talk with him about some relaxing topics or recall some beautiful past events. If you feel unable to face your ex-husband, you can also decline his invitation and keep your distance and independence.