My ex-boyfriend's grandfather died, and I sent him a message of comfort, but he didn't reply. What should I do at this time? We can't meet again, so we can't.

Because your ex-boyfriend's grandfather died, you can't go to their house anymore, because you and he belong to an ex-relationship. If you go, it will have a certain impact on his current position and may destroy their feelings, so you can't go.

And now that you have sent a message to the other party, if the other party doesn't reply at this time, it may be that the other party is too busy, but you have already done it here, so you are doing it perfectly now, and you don't need to consider the next step.

And the other person will thank you especially when he sees your information, because you are a sentimental person, so he will feel guilty.

But you must never have any contact, because you both have your own incumbents now, and you can't destroy your feelings.