After online dating, she suddenly didn't return messages or phone calls.

There are two possibilities. The first is that something happened to her. She was upset and didn't want to talk. She just wants to be quiet. Maybe she doesn't need comfort at this time. She needs to be quiet, not dislike you. She doesn't want to talk to you.

The second possibility is that she doesn't like you. Maybe she is beginning to understand that online dating is useless. She doesn't like you at all, but regards you as a dependence, what's more, this dependence is unreliable.

It's best not to disturb her. If she is just upset and wants to be quiet, then she will come to you when she is upset.

If she really doesn't like you, then don't bother her and ask her why, or she will find you annoying. Originally, she felt sorry for you, but when you bothered her again, the good impression you gave her was all gone.

Please forgive me. Step by step. You can't force your feelings.