Why doesn't he enter the app?

I was talking to a guy on an app. He used to immediately read my messages every day, but he hasn't entered the app since April 2nd. I sent a message on April 10th and he still hasn't been entering. Only my message was delivered to him. He just doesn't enter the app. I'm tired of cliche sentences like "He has a girlfriend or something." If so, why would he immediately read my messages every day or didn't delete me completely? In fact, he would tell me that he felt depressed all the time.
Why doesn't he enter the app?
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